In this post, we will look at a basic multi-area OSPF configuration. If you haven’t already, it would be worth a quick review of the single-area configuration.
This example is relevant to all Junos-based devices – M, T, MX, PTX, SRX, EX, and QFX.
In the examples that follow, we will extend an existing OSPF network by adding two new normal areas to it.
The configuration is simple and adds additional interfaces to the OSPF configuration, but places them under a different area.
set protocols ospf area <<area>> interface <<interface>>Lab Environment
The lab environment uses logical systems. These are connected using logical tunnel (lt-) interfaces.
- R1 through R10 are configured using logical systems
- R3 through R8 are already configured for area 0.
- R3 through R8 have their OSPF interfaces set as point-to-point (p2p).
- All routers have a loopback interface configured, and a router-id set.
- All the interfaces are already configured.
The configuration and show commands listed below are done with the ‘cli logical-system’ set to be the relevant logical system. This means commands don’t need to refer to which logical system to run the command against. This makes the output the same as if we were not using logical systems.
Here is an example showing the configuration of R3 before we start.
lab@vRouter-1:R3> show configuration
interfaces {
lt-0/0/0 {
unit 4 {
encapsulation ethernet;
peer-unit 3;
family inet {
address 172.16.13.2/24;
}
}
unit 7 {
encapsulation ethernet;
peer-unit 8;
family inet {
address 172.16.34.1/24;
}
}
unit 9 {
encapsulation ethernet;
peer-unit 10;
family inet {
address 172.16.35.1/24;
}
}
}
lo0 {
unit 3 {
family inet {
address 192.168.0.3/32;
}
}
}
}
protocols {
ospf {
area 0.0.0.0 {
interface lt-0/0/0.7 {
interface-type p2p;
}
interface lt-0/0/0.9 {
interface-type p2p;
}
interface lo0.3 {
passive;
}
}
reference-bandwidth 100g;
}
}
routing-options {
router-id 192.168.0.3;
}
lab@vRouter-1:R3>And here is some OSPF output to validate the current network
lab@vRouter-1:R3> show ospf interface
Interface State Area DR ID BDR ID Nbrs
lo0.3 DRother 0.0.0.0 0.0.0.0 0.0.0.0 0
lt-0/0/0.7 PtToPt 0.0.0.0 0.0.0.0 0.0.0.0 1
lt-0/0/0.9 PtToPt 0.0.0.0 0.0.0.0 0.0.0.0 1
lab@vRouter-1:R3> show ospf neighbor
Address Interface State ID Pri Dead
172.16.34.2 lt-0/0/0.7 Full 192.168.0.4 128 34
172.16.35.2 lt-0/0/0.9 Full 192.168.0.5 128 35
lab@vRouter-1:R3> show route protocol ospf
inet.0: 18 destinations, 18 routes (18 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
172.16.46.0/24 *[OSPF/10] 00:11:09, metric 2
> to 172.16.34.2 via lt-0/0/0.7
172.16.56.0/24 *[OSPF/10] 00:10:59, metric 2
> to 172.16.35.2 via lt-0/0/0.9
172.16.57.0/24 *[OSPF/10] 00:10:59, metric 2
> to 172.16.35.2 via lt-0/0/0.9
172.16.68.0/24 *[OSPF/10] 00:10:59, metric 3
to 172.16.34.2 via lt-0/0/0.7
> to 172.16.35.2 via lt-0/0/0.9
172.16.78.0/24 *[OSPF/10] 00:10:59, metric 3
> to 172.16.35.2 via lt-0/0/0.9
192.168.0.4/32 *[OSPF/10] 00:11:09, metric 1
> to 172.16.34.2 via lt-0/0/0.7
192.168.0.5/32 *[OSPF/10] 00:10:59, metric 1
> to 172.16.35.2 via lt-0/0/0.9
192.168.0.6/32 *[OSPF/10] 00:10:59, metric 2
to 172.16.34.2 via lt-0/0/0.7
> to 172.16.35.2 via lt-0/0/0.9
192.168.0.7/32 *[OSPF/10] 00:10:59, metric 2
> to 172.16.35.2 via lt-0/0/0.9
192.168.0.8/32 *[OSPF/10] 00:10:59, metric 3
> to 172.16.34.2 via lt-0/0/0.7
to 172.16.35.2 via lt-0/0/0.9
224.0.0.5/32 *[OSPF/10] 00:11:19, metric 1
MultiRecv
inet6.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)
lab@vRouter-1:R3> show ospf database
OSPF database, Area 0.0.0.0
Type ID Adv Rtr Seq Age Opt Cksum Len
Router *192.168.0.3 192.168.0.3 0x80000003 684 0x22 0x4a06 84
Router 192.168.0.4 192.168.0.4 0x80000002 690 0x22 0x989e 84
Router 192.168.0.5 192.168.0.5 0x80000004 680 0x22 0x326c 108
Router 192.168.0.6 192.168.0.6 0x80000003 686 0x22 0xb3ba 108
Router 192.168.0.7 192.168.0.7 0x80000002 691 0x22 0xab1 84
Router 192.168.0.8 192.168.0.8 0x80000002 692 0x22 0x9e03 84
lab@vRouter-1:R3>Because we have set all the interfaces as point-to-point, we only see Router LSAs, there are no network LSAs present in the OSPF database.
Next, we’ll move on to configuring area 1.
R3 Configuration – Area 1
Since R3 has area 0 already configured, we just need to configure the lt-0/0/0.4 interface under area 1.
lab@vRouter-1:R3> configure
Entering configuration mode
[edit]
lab@vRouter-1:R3# show protocols ospf
area 0.0.0.0 {
interface lt-0/0/0.7 {
interface-type p2p;
}
interface lt-0/0/0.9 {
interface-type p2p;
}
interface lo0.3 {
passive;
}
}
reference-bandwidth 100g;
[edit]
lab@vRouter-1:R3# set protocols ospf area 1 interface lt-0/0/0.4 interface-type p2p
[edit]
lab@vRouter-1:R3# show protocols ospf
area 0.0.0.0 {
interface lt-0/0/0.7 {
interface-type p2p;
}
interface lt-0/0/0.9 {
interface-type p2p;
}
interface lo0.3 {
passive;
}
}
area 0.0.0.1 {
interface lt-0/0/0.4 {
interface-type p2p;
}
}
reference-bandwidth 100g;
[edit]
lab@vRouter-1:R3# commit
commit complete
[edit]
lab@vRouter-1:R3#R4 Configuration – Area 1
R4 is similar to R3. We just need to add the interface to area 1.
lab@vRouter-1:R4> configure
Entering configuration mode
[edit]
lab@vRouter-1:R4# show protocols ospf
area 0.0.0.0 {
interface lo0.4 {
passive;
}
interface lt-0/0/0.8 {
interface-type p2p;
}
interface lt-0/0/0.11 {
interface-type p2p;
}
}
reference-bandwidth 100g;
[edit]
lab@vRouter-1:R4# set protocols ospf area 1 interface lt-0/0/0.6 interface-type p2p
[edit]
lab@vRouter-1:R4# show protocols ospf
area 0.0.0.0 {
interface lo0.4 {
passive;
}
interface lt-0/0/0.8 {
interface-type p2p;
}
interface lt-0/0/0.11 {
interface-type p2p;
}
}
area 0.0.0.1 {
interface lt-0/0/0.6 {
interface-type p2p;
}
}
reference-bandwidth 100g;
[edit]
lab@vRouter-1:R4# commit and-quit
commit complete
Exiting configuration mode
lab@vRouter-1:R4>R1 Configuration – Area 1
R1 doesn’t have any OSPF configuration to start with. It will be an area internal router. We’ll configure the interface facing R3 as point-to-point but leave the interface facing R2 as a broadcast network so we’ll have a network LSA in area 1.
[edit]
lab@vRouter-1:R1# show protocols ospf
[edit]
lab@vRouter-1:R1# set protocols ospf reference-bandwidth 100g
[edit]
lab@vRouter-1:R1# set protocols ospf area 1 interface lo0.1 passive
[edit]
lab@vRouter-1:R1# set protocols ospf area 1 interface lt-0/0/0.3 interface-type p2p
[edit]
lab@vRouter-1:R1# set protocols ospf area 1 interface lt-0/0/0.1
[edit]
lab@vRouter-1:R1# show protocols ospf
area 0.0.0.1 {
interface lo0.1 {
passive;
}
interface lt-0/0/0.3 {
interface-type p2p;
}
interface lt-0/0/0.1;
}
reference-bandwidth 100g;
[edit]
lab@vRouter-1:R1# commit
commit complete
[edit]
lab@vRouter-1:R1#R2 Configuration – Area 1
The configuration for R2 is shown below. This is similar to the R1 configuration.
[edit]
lab@vRouter-1:R2# show protocols ospf
area 0.0.0.1 {
interface lt-0/0/0.5 {
interface-type p2p;
}
interface lt-0/0/0.2;
interface lo0.2 {
passive;
}
}
reference-bandwidth 100g;
[edit]
lab@vRouter-1:R2#Area 1 Validation
Validation From R1
First, let’s look at the OSPF interfaces and neighbors.
lab@vRouter-1:R1> show ospf interface
Interface State Area DR ID BDR ID Nbrs
lo0.1 DRother 0.0.0.1 0.0.0.0 0.0.0.0 0
lt-0/0/0.1 BDR 0.0.0.1 192.168.0.2 192.168.0.1 1
lt-0/0/0.3 PtToPt 0.0.0.1 0.0.0.0 0.0.0.0 1
lab@vRouter-1:R1> show ospf neighbor
Address Interface State ID Pri Dead
172.16.12.2 lt-0/0/0.1 Full 192.168.0.2 128 39
172.16.13.2 lt-0/0/0.3 Full 192.168.0.3 128 35
lab@vRouter-1:R1> As you might expect, the interfaces are all in area 1. The link from R1 to R2 has selected R2 as the DR to advertise the Network LSA.
R1 has two neighbors.
Next, we’ll check the OSPF database.
lab@vRouter-1:R1> show ospf database
OSPF database, Area 0.0.0.1
Type ID Adv Rtr Seq Age Opt Cksum Len
Router *192.168.0.1 192.168.0.1 0x80000006 529 0x22 0xc563 72
Router 192.168.0.2 192.168.0.2 0x80000004 525 0x22 0x8986 72
Router 192.168.0.3 192.168.0.3 0x80000002 941 0x22 0x2820 48
Router 192.168.0.4 192.168.0.4 0x80000002 699 0x22 0x9995 48
Network 172.16.12.2 192.168.0.2 0x80000001 530 0x22 0x46e7 32
Summary 172.16.34.0 192.168.0.3 0x80000001 1234 0x22 0x7878 28
Summary 172.16.34.0 192.168.0.4 0x80000001 1092 0x22 0x727d 28
Summary 172.16.35.0 192.168.0.3 0x80000001 1234 0x22 0x6d82 28
Summary 172.16.35.0 192.168.0.4 0x80000002 323 0x22 0x6f7d 28
Summary 172.16.46.0 192.168.0.3 0x80000002 599 0x22 0xfbe6 28
Summary 172.16.46.0 192.168.0.4 0x80000001 1092 0x22 0xedf5 28
Summary 172.16.56.0 192.168.0.3 0x80000002 437 0x22 0x8d4b 28
Summary 172.16.56.0 192.168.0.4 0x80000002 173 0x22 0x8750 28
Summary 172.16.57.0 192.168.0.3 0x80000002 275 0x22 0x8255 28
Summary 172.16.57.0 192.168.0.4 0x80000002 24 0x22 0x864f 28
Summary 172.16.68.0 192.168.0.3 0x80000002 126 0x22 0x13b8 28
Summary 172.16.68.0 192.168.0.4 0x80000001 1092 0x22 0x5c7 28
Summary 172.16.78.0 192.168.0.3 0x80000001 1234 0x22 0xa61c 28
Summary 172.16.78.0 192.168.0.4 0x80000001 1092 0x22 0xa021 28
Summary 192.168.0.3 192.168.0.3 0x80000001 1234 0x22 0x9bc8 28
Summary 192.168.0.3 192.168.0.4 0x80000001 1092 0x22 0x9fc2 28
Summary 192.168.0.4 192.168.0.3 0x80000001 1234 0x22 0x9bc6 28
Summary 192.168.0.4 192.168.0.4 0x80000001 1092 0x22 0x8bd6 28
Summary 192.168.0.5 192.168.0.3 0x80000001 1234 0x22 0x91cf 28
Summary 192.168.0.5 192.168.0.4 0x80000001 1092 0x22 0x95c9 28
Summary 192.168.0.6 192.168.0.3 0x80000001 1234 0x22 0x91cd 28
Summary 192.168.0.6 192.168.0.4 0x80000001 1092 0x22 0x81dd 28
Summary 192.168.0.7 192.168.0.3 0x80000001 1234 0x22 0x87d6 28
Summary 192.168.0.7 192.168.0.4 0x80000001 1092 0x22 0x8bd0 28
Summary 192.168.0.8 192.168.0.3 0x80000001 1234 0x22 0x87d4 28
Summary 192.168.0.8 192.168.0.4 0x80000001 1092 0x22 0x77e4 28
lab@vRouter-1:R1>First, we have four Router LSAs and one Network LSA, which are internal to Area 1. Next, we have a lot of Summary LSAs representing the information from area 0. Since both R3 and R4 are acting as ABRs, they both announce summary LSAs into area 1.
The routing table is shown below.
lab@vRouter-1:R1> show route table inet.0
inet.0: 21 destinations, 21 routes (21 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
172.16.12.0/24 *[Direct/0] 01:45:14
> via lt-0/0/0.1
172.16.12.1/32 *[Local/0] 01:45:14
Local via lt-0/0/0.1
172.16.13.0/24 *[Direct/0] 01:45:13
> via lt-0/0/0.3
172.16.13.1/32 *[Local/0] 01:45:13
Local via lt-0/0/0.3
172.16.24.0/24 *[OSPF/10] 00:12:01, metric 2
> to 172.16.12.2 via lt-0/0/0.1
172.16.34.0/24 *[OSPF/10] 00:18:55, metric 2
> to 172.16.13.2 via lt-0/0/0.3
172.16.35.0/24 *[OSPF/10] 00:18:55, metric 2
> to 172.16.13.2 via lt-0/0/0.3
172.16.46.0/24 *[OSPF/10] 00:12:01, metric 3
> to 172.16.12.2 via lt-0/0/0.1
to 172.16.13.2 via lt-0/0/0.3
172.16.56.0/24 *[OSPF/10] 00:18:55, metric 3
> to 172.16.13.2 via lt-0/0/0.3
172.16.57.0/24 *[OSPF/10] 00:18:55, metric 3
> to 172.16.13.2 via lt-0/0/0.3
172.16.68.0/24 *[OSPF/10] 00:12:01, metric 4
to 172.16.12.2 via lt-0/0/0.1
> to 172.16.13.2 via lt-0/0/0.3
172.16.78.0/24 *[OSPF/10] 00:18:55, metric 4
> to 172.16.13.2 via lt-0/0/0.3
192.168.0.1/32 *[Direct/0] 01:45:14
> via lo0.1
192.168.0.2/32 *[OSPF/10] 00:12:01, metric 1
> to 172.16.12.2 via lt-0/0/0.1
192.168.0.3/32 *[OSPF/10] 00:18:55, metric 1
> to 172.16.13.2 via lt-0/0/0.3
192.168.0.4/32 *[OSPF/10] 00:12:01, metric 2
to 172.16.12.2 via lt-0/0/0.1
> to 172.16.13.2 via lt-0/0/0.3
192.168.0.5/32 *[OSPF/10] 00:18:55, metric 2
> to 172.16.13.2 via lt-0/0/0.3
192.168.0.6/32 *[OSPF/10] 00:12:01, metric 3
to 172.16.12.2 via lt-0/0/0.1
> to 172.16.13.2 via lt-0/0/0.3
192.168.0.7/32 *[OSPF/10] 00:18:55, metric 3
> to 172.16.13.2 via lt-0/0/0.3
192.168.0.8/32 *[OSPF/10] 00:12:01, metric 4
> to 172.16.12.2 via lt-0/0/0.1
to 172.16.13.2 via lt-0/0/0.3
224.0.0.5/32 *[OSPF/10] 00:19:00, metric 1
MultiRecv
lab@vRouter-1:R1>You may notice that some routes have two available next hops. Since we have not configured any sort of load-balancing, the default behavior is that for each route, Junos will pick one of the paths to use.
Validation From R3
The validation from R3 is a bit different. It acts as an ABR and has interfaces in two areas.
lab@vRouter-1:R3> show ospf interface
Interface State Area DR ID BDR ID Nbrs
lo0.3 DRother 0.0.0.0 0.0.0.0 0.0.0.0 0
lt-0/0/0.7 PtToPt 0.0.0.0 0.0.0.0 0.0.0.0 1
lt-0/0/0.9 PtToPt 0.0.0.0 0.0.0.0 0.0.0.0 1
lt-0/0/0.4 PtToPt 0.0.0.1 0.0.0.0 0.0.0.0 1
lab@vRouter-1:R3> show ospf neighbor
Address Interface State ID Pri Dead
172.16.34.2 lt-0/0/0.7 Full 192.168.0.4 128 31
172.16.35.2 lt-0/0/0.9 Full 192.168.0.5 128 32
172.16.13.1 lt-0/0/0.4 Full 192.168.0.1 128 32
lab@vRouter-1:R3>When we show the OSPF database on R3, we see the output is broken into different areas.
lab@vRouter-1:R3> show ospf database
OSPF database, Area 0.0.0.0
Type ID Adv Rtr Seq Age Opt Cksum Len
Router *192.168.0.3 192.168.0.3 0x80000005 1538 0x22 0x4904 84
Router 192.168.0.4 192.168.0.4 0x80000004 1259 0x22 0x979c 84
Router 192.168.0.5 192.168.0.5 0x80000005 210 0x22 0x306d 108
Router 192.168.0.6 192.168.0.6 0x80000004 216 0x22 0xb1bb 108
Router 192.168.0.7 192.168.0.7 0x80000003 221 0x22 0x8b2 84
Router 192.168.0.8 192.168.0.8 0x80000003 222 0x22 0x9c04 84
Summary *172.16.12.0 192.168.0.3 0x80000002 1021 0x22 0x7391 28
Summary 172.16.12.0 192.168.0.4 0x80000001 1183 0x22 0x6f95 28
Summary *172.16.13.0 192.168.0.3 0x80000002 1258 0x22 0x5ea6 28
Summary 172.16.13.0 192.168.0.4 0x80000002 1016 0x22 0x6c95 28
Summary *172.16.24.0 192.168.0.3 0x80000002 1015 0x22 0xf8fe 28
Summary 172.16.24.0 192.168.0.4 0x80000002 971 0x22 0xde1a 28
Summary *192.168.0.1 192.168.0.3 0x80000001 1093 0x22 0xb9ab 28
Summary 192.168.0.1 192.168.0.4 0x80000002 1016 0x22 0xbba6 28
Summary *192.168.0.2 192.168.0.3 0x80000002 1015 0x22 0xb7aa 28
Summary 192.168.0.2 192.168.0.4 0x80000001 1185 0x22 0xa9b9 28
OSPF database, Area 0.0.0.1
Type ID Adv Rtr Seq Age Opt Cksum Len
Router 192.168.0.1 192.168.0.1 0x80000006 1024 0x22 0xc563 72
Router 192.168.0.2 192.168.0.2 0x80000004 1020 0x22 0x8986 72
Router *192.168.0.3 192.168.0.3 0x80000002 1434 0x22 0x2820 48
Router 192.168.0.4 192.168.0.4 0x80000002 1194 0x22 0x9995 48
Network 172.16.12.2 192.168.0.2 0x80000001 1025 0x22 0x46e7 32
Summary *172.16.34.0 192.168.0.3 0x80000001 1728 0x22 0x7878 28
Summary 172.16.34.0 192.168.0.4 0x80000001 1587 0x22 0x727d 28
Summary *172.16.35.0 192.168.0.3 0x80000001 1728 0x22 0x6d82 28
Summary 172.16.35.0 192.168.0.4 0x80000002 818 0x22 0x6f7d 28
Summary *172.16.46.0 192.168.0.3 0x80000002 1092 0x22 0xfbe6 28
Summary 172.16.46.0 192.168.0.4 0x80000001 1587 0x22 0xedf5 28
Summary *172.16.56.0 192.168.0.3 0x80000002 930 0x22 0x8d4b 28
Summary 172.16.56.0 192.168.0.4 0x80000002 668 0x22 0x8750 28
Summary *172.16.57.0 192.168.0.3 0x80000002 768 0x22 0x8255 28
Summary 172.16.57.0 192.168.0.4 0x80000002 519 0x22 0x864f 28
Summary *172.16.68.0 192.168.0.3 0x80000002 619 0x22 0x13b8 28
Summary 172.16.68.0 192.168.0.4 0x80000002 369 0x22 0x3c8 28
Summary *172.16.78.0 192.168.0.3 0x80000002 469 0x22 0xa41d 28
Summary 172.16.78.0 192.168.0.4 0x80000002 219 0x22 0x9e22 28
Summary *192.168.0.3 192.168.0.3 0x80000001 1728 0x22 0x9bc8 28
Summary 192.168.0.3 192.168.0.4 0x80000002 69 0x22 0x9dc3 28
Summary *192.168.0.4 192.168.0.3 0x80000002 320 0x22 0x99c7 28
Summary 192.168.0.4 192.168.0.4 0x80000001 1587 0x22 0x8bd6 28
Summary *192.168.0.5 192.168.0.3 0x80000002 171 0x22 0x8fd0 28
Summary 192.168.0.5 192.168.0.4 0x80000001 1587 0x22 0x95c9 28
Summary *192.168.0.6 192.168.0.3 0x80000002 21 0x22 0x8fce 28
Summary 192.168.0.6 192.168.0.4 0x80000001 1587 0x22 0x81dd 28
Summary *192.168.0.7 192.168.0.3 0x80000001 1728 0x22 0x87d6 28
Summary 192.168.0.7 192.168.0.4 0x80000001 1587 0x22 0x8bd0 28
Summary *192.168.0.8 192.168.0.3 0x80000001 1728 0x22 0x87d4 28
Summary 192.168.0.8 192.168.0.4 0x80000001 1587 0x22 0x77e4 28
lab@vRouter-1:R3>Area 0 now has ten summary LSAs. Five each from R3 and R4 which are acting as ABRs.
The routing table for R3 is shown below.
lab@vRouter-1:R3> show route table inet.0
inet.0: 22 destinations, 22 routes (22 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
172.16.12.0/24 *[OSPF/10] 00:19:41, metric 2
> to 172.16.13.1 via lt-0/0/0.4
172.16.13.0/24 *[Direct/0] 01:52:48
> via lt-0/0/0.4
172.16.13.2/32 *[Local/0] 01:52:48
Local via lt-0/0/0.4
172.16.24.0/24 *[OSPF/10] 00:19:35, metric 3
> to 172.16.13.1 via lt-0/0/0.4
172.16.34.0/24 *[Direct/0] 01:52:47
> via lt-0/0/0.7
172.16.34.1/32 *[Local/0] 01:52:47
Local via lt-0/0/0.7
172.16.35.0/24 *[Direct/0] 01:52:47
> via lt-0/0/0.9
172.16.35.1/32 *[Local/0] 01:52:47
Local via lt-0/0/0.9
172.16.46.0/24 *[OSPF/10] 00:56:15, metric 2
> to 172.16.34.2 via lt-0/0/0.7
172.16.56.0/24 *[OSPF/10] 00:56:05, metric 2
> to 172.16.35.2 via lt-0/0/0.9
172.16.57.0/24 *[OSPF/10] 00:56:05, metric 2
> to 172.16.35.2 via lt-0/0/0.9
172.16.68.0/24 *[OSPF/10] 00:56:05, metric 3
to 172.16.34.2 via lt-0/0/0.7
> to 172.16.35.2 via lt-0/0/0.9
172.16.78.0/24 *[OSPF/10] 00:56:05, metric 3
> to 172.16.35.2 via lt-0/0/0.9
192.168.0.1/32 *[OSPF/10] 00:20:53, metric 1
> to 172.16.13.1 via lt-0/0/0.4
192.168.0.2/32 *[OSPF/10] 00:19:35, metric 2
> to 172.16.13.1 via lt-0/0/0.4
192.168.0.3/32 *[Direct/0] 01:52:48
> via lo0.3
192.168.0.4/32 *[OSPF/10] 00:56:15, metric 1
> to 172.16.34.2 via lt-0/0/0.7
192.168.0.5/32 *[OSPF/10] 00:56:05, metric 1
> to 172.16.35.2 via lt-0/0/0.9
192.168.0.6/32 *[OSPF/10] 00:56:05, metric 2
to 172.16.34.2 via lt-0/0/0.7
> to 172.16.35.2 via lt-0/0/0.9
192.168.0.7/32 *[OSPF/10] 00:56:05, metric 2
> to 172.16.35.2 via lt-0/0/0.9
192.168.0.8/32 *[OSPF/10] 00:56:05, metric 3
> to 172.16.34.2 via lt-0/0/0.7
to 172.16.35.2 via lt-0/0/0.9
224.0.0.5/32 *[OSPF/10] 00:56:25, metric 1
MultiRecv
lab@vRouter-1:R3>R7 through R10 Configuration – Area 2
The OSPF configuration for R7 through R10 is similar to that for R1 through R4. In this case, R9 and R10 are the area 2 internal routers, and R7 and R8 are the ABRs.
For brevity, I’ll just show the OSPF stanza for each router.
R7:
[edit]
lab@vRouter-1:R7# show protocols ospf
area 0.0.0.0 {
interface lo0.7 {
passive;
}
interface lt-0/0/0.16 {
interface-type p2p;
}
interface lt-0/0/0.19 {
interface-type p2p;
}
}
area 0.0.0.2 {
interface lt-0/0/0.21 {
interface-type p2p;
}
}
reference-bandwidth 100g;
[edit]
lab@vRouter-1:R7#R8:
[edit]
lab@vRouter-1:R8# show protocols ospf
area 0.0.0.0 {
interface lo0.8 {
passive;
}
interface lt-0/0/0.18 {
interface-type p2p;
}
interface lt-0/0/0.20 {
interface-type p2p;
}
}
area 0.0.0.2 {
interface lt-0/0/0.23 {
interface-type p2p;
}
}
reference-bandwidth 100g;
[edit]
lab@vRouter-1:R8#R9:
[edit]
lab@vRouter-1:R9# show protocols ospf
area 0.0.0.2 {
interface lo0.9 {
passive;
}
interface lt-0/0/0.22 {
interface-type p2p;
}
interface lt-0/0/0.25;
}
reference-bandwidth 100g;
[edit]
lab@vRouter-1:R9#R10:
[edit]
lab@vRouter-1:R10# show protocols ospf
area 0.0.0.2 {
interface lo0.10 {
passive;
}
interface lt-0/0/0.24 {
interface-type p2p;
}
interface lt-0/0/0.26;
}
reference-bandwidth 100g;
[edit]
lab@vRouter-1:R10# Area 2 Validation
Validation From R9
First, we’ll check the OSPF interface and neighbors.
lab@vRouter-1:R9> show ospf interface
Interface State Area DR ID BDR ID Nbrs
lo0.9 DRother 0.0.0.2 0.0.0.0 0.0.0.0 0
lt-0/0/0.22 PtToPt 0.0.0.2 0.0.0.0 0.0.0.0 1
lt-0/0/0.25 DR 0.0.0.2 192.168.0.9 192.168.0.10 1
lab@vRouter-1:R9> show ospf neighbor
Address Interface State ID Pri Dead
172.16.79.1 lt-0/0/0.22 Full 192.168.0.7 128 38
172.16.190.2 lt-0/0/0.25 Full 192.168.0.10 128 35
lab@vRouter-1:R9>As R9 is an internal area router, it only sees the OSPF database for Area 2. Once again, we have two ABRs, both advertising summaries for the other areas.
lab@vRouter-1:R9> show ospf database
OSPF database, Area 0.0.0.2
Type ID Adv Rtr Seq Age Opt Cksum Len
Router 192.168.0.7 192.168.0.7 0x80000002 406 0x22 0xf6bd 48
Router 192.168.0.8 192.168.0.8 0x80000002 406 0x22 0x687e 48
Router *192.168.0.9 192.168.0.9 0x80000003 83 0x22 0x62c3 72
Router 192.168.0.10 192.168.0.10 0x80000003 84 0x22 0x9db8 72
Network *172.16.190.1 192.168.0.9 0x80000001 83 0x22 0x3d28 32
Summary 172.16.12.0 192.168.0.7 0x80000001 406 0x22 0x718e 28
Summary 172.16.12.0 192.168.0.8 0x80000001 406 0x22 0x6b93 28
Summary 172.16.13.0 192.168.0.7 0x80000001 406 0x22 0x5ca3 28
Summary 172.16.13.0 192.168.0.8 0x80000001 406 0x22 0x609d 28
Summary 172.16.24.0 192.168.0.7 0x80000001 406 0x22 0xec07 28
Summary 172.16.24.0 192.168.0.8 0x80000001 406 0x22 0xdc17 28
Summary 172.16.34.0 192.168.0.7 0x80000001 406 0x22 0x7476 28
Summary 172.16.34.0 192.168.0.8 0x80000001 406 0x22 0x6e7b 28
Summary 172.16.35.0 192.168.0.7 0x80000001 406 0x22 0x5f8b 28
Summary 172.16.35.0 192.168.0.8 0x80000001 406 0x22 0x6385 28
Summary 172.16.46.0 192.168.0.7 0x80000001 406 0x22 0xefee 28
Summary 172.16.46.0 192.168.0.8 0x80000001 406 0x22 0xdffe 28
Summary 172.16.56.0 192.168.0.7 0x80000001 406 0x22 0x775e 28
Summary 172.16.56.0 192.168.0.8 0x80000001 406 0x22 0x7163 28
Summary 172.16.57.0 192.168.0.7 0x80000001 406 0x22 0x6273 28
Summary 172.16.57.0 192.168.0.8 0x80000001 406 0x22 0x666d 28
Summary 172.16.68.0 192.168.0.7 0x80000001 406 0x22 0xf2d6 28
Summary 172.16.68.0 192.168.0.8 0x80000001 406 0x22 0xe2e6 28
Summary 172.16.78.0 192.168.0.7 0x80000001 406 0x22 0x7a46 28
Summary 172.16.78.0 192.168.0.8 0x80000001 406 0x22 0x744b 28
Summary 192.168.0.1 192.168.0.7 0x80000001 406 0x22 0xb5a9 28
Summary 192.168.0.1 192.168.0.8 0x80000001 406 0x22 0xb9a3 28
Summary 192.168.0.2 192.168.0.7 0x80000001 406 0x22 0xb5a7 28
Summary 192.168.0.2 192.168.0.8 0x80000001 406 0x22 0xa5b7 28
Summary 192.168.0.3 192.168.0.7 0x80000001 406 0x22 0x97c6 28
Summary 192.168.0.3 192.168.0.8 0x80000001 406 0x22 0x9bc0 28
Summary 192.168.0.4 192.168.0.7 0x80000001 406 0x22 0x97c4 28
Summary 192.168.0.4 192.168.0.8 0x80000001 406 0x22 0x87d4 28
Summary 192.168.0.5 192.168.0.7 0x80000001 406 0x22 0x79e3 28
Summary 192.168.0.5 192.168.0.8 0x80000001 406 0x22 0x7ddd 28
Summary 192.168.0.6 192.168.0.7 0x80000001 406 0x22 0x79e1 28
Summary 192.168.0.6 192.168.0.8 0x80000001 406 0x22 0x69f1 28
Summary 192.168.0.7 192.168.0.7 0x80000001 406 0x22 0x5b01 28
Summary 192.168.0.7 192.168.0.8 0x80000001 406 0x22 0x5ffa 28
Summary 192.168.0.8 192.168.0.7 0x80000001 406 0x22 0x5bfe 28
Summary 192.168.0.8 192.168.0.8 0x80000001 406 0x22 0x4b0f 28
lab@vRouter-1:R9> Since we’ve now got the full OSPF network in place, we can ping and traceroute from R9’s loopback to the loopbacks of R1 and R2.
lab@vRouter-1:R9> ping 192.168.0.1 source 192.168.0.9 count 2
PING 192.168.0.1 (192.168.0.1): 56 data bytes
64 bytes from 192.168.0.1: icmp_seq=0 ttl=61 time=2.935 ms
64 bytes from 192.168.0.1: icmp_seq=1 ttl=61 time=456.195 ms
--- 192.168.0.1 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max/stddev = 2.935/229.565/456.195/226.630 ms
lab@vRouter-1:R9> traceroute 192.168.0.1 source 192.168.0.9
traceroute to 192.168.0.1 (192.168.0.1) from 192.168.0.9, 30 hops max, 52 byte packets
1 172.16.79.1 (172.16.79.1) 18.063 ms 11.819 ms 7.889 ms
2 172.16.57.1 (172.16.57.1) 6.906 ms 12.994 ms 4.581 ms
3 172.16.35.1 (172.16.35.1) 11.152 ms 6.661 ms 4.786 ms
4 192.168.0.1 (192.168.0.1) 4.105 ms 8.805 ms 7.889 ms
lab@vRouter-1:R9> ping 192.168.0.2 source 192.168.0.9 count 2
PING 192.168.0.2 (192.168.0.2): 56 data bytes
64 bytes from 192.168.0.2: icmp_seq=0 ttl=60 time=3.969 ms
64 bytes from 192.168.0.2: icmp_seq=1 ttl=60 time=2.403 ms
--- 192.168.0.2 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max/stddev = 2.403/3.186/3.969/0.783 ms
lab@vRouter-1:R9> traceroute 192.168.0.2 source 192.168.0.9
traceroute to 192.168.0.2 (192.168.0.2) from 192.168.0.9, 30 hops max, 52 byte packets
1 172.16.190.2 (172.16.190.2) 5.968 ms 7.041 ms 5.213 ms
2 172.16.180.1 (172.16.180.1) 5.089 ms 4.753 ms 2.876 ms
3 172.16.68.1 (172.16.68.1) 2.560 ms 4.276 ms 2.622 ms
4 172.16.46.1 (172.16.46.1) 3.076 ms 3.365 ms 3.347 ms
5 192.168.0.2 (192.168.0.2) 4.785 ms 4.756 ms 5.262 ms
lab@vRouter-1:R9>Validation From R7
The OSPF interface shows interfaces in two different areas. The neighbor output shows three neighbors.
lab@vRouter-1:R7> show ospf interface
Interface State Area DR ID BDR ID Nbrs
lo0.7 DRother 0.0.0.0 0.0.0.0 0.0.0.0 0
lt-0/0/0.16 PtToPt 0.0.0.0 0.0.0.0 0.0.0.0 1
lt-0/0/0.19 PtToPt 0.0.0.0 0.0.0.0 0.0.0.0 1
lt-0/0/0.21 PtToPt 0.0.0.2 0.0.0.0 0.0.0.0 1
lab@vRouter-1:R7> show ospf neighbor
Address Interface State ID Pri Dead
172.16.57.1 lt-0/0/0.16 Full 192.168.0.5 128 31
172.16.78.2 lt-0/0/0.19 Full 192.168.0.8 128 32
172.16.79.2 lt-0/0/0.21 Full 192.168.0.9 128 31
lab@vRouter-1:R7>The output for the OSPF database on R7 is growing larger. R7 sees the database for both area 0 and area 2.
lab@vRouter-1:R7> show ospf database
OSPF database, Area 0.0.0.0
Type ID Adv Rtr Seq Age Opt Cksum Len
Router 192.168.0.3 192.168.0.3 0x80000005 2712 0x22 0x4904 84
Router 192.168.0.4 192.168.0.4 0x80000004 2433 0x22 0x979c 84
Router 192.168.0.5 192.168.0.5 0x80000005 1382 0x22 0x306d 108
Router 192.168.0.6 192.168.0.6 0x80000004 1388 0x22 0xb1bb 108
Router *192.168.0.7 192.168.0.7 0x80000005 384 0x22 0x7b0 84
Router 192.168.0.8 192.168.0.8 0x80000005 385 0x22 0x9b02 84
Summary 172.16.12.0 192.168.0.3 0x80000002 2195 0x22 0x7391 28
Summary 172.16.12.0 192.168.0.4 0x80000001 2357 0x22 0x6f95 28
...
<<Output removed for brevity>>
...
Summary *192.168.0.9 192.168.0.7 0x80000001 680 0x22 0x5108 28
Summary 192.168.0.9 192.168.0.8 0x80000001 366 0x22 0x5502 28
Summary *192.168.0.10 192.168.0.7 0x80000001 365 0x22 0x5106 28
Summary 192.168.0.10 192.168.0.8 0x80000001 681 0x22 0x4116 28
OSPF database, Area 0.0.0.2
Type ID Adv Rtr Seq Age Opt Cksum Len
Router *192.168.0.7 192.168.0.7 0x80000002 687 0x22 0xf6bd 48
Router 192.168.0.8 192.168.0.8 0x80000002 689 0x22 0x687e 48
Router 192.168.0.9 192.168.0.9 0x80000003 366 0x22 0x62c3 72
Router 192.168.0.10 192.168.0.10 0x80000003 367 0x22 0x9db8 72
Network 172.16.190.1 192.168.0.9 0x80000001 366 0x22 0x3d28 32
Summary *172.16.12.0 192.168.0.7 0x80000002 271 0x22 0x6f8f 28
Summary 172.16.12.0 192.168.0.8 0x80000002 274 0x22 0x6994 28
Summary *172.16.13.0 192.168.0.7 0x80000002 159 0x22 0x5aa4 28
Summary 172.16.13.0 192.168.0.8 0x80000002 162 0x22 0x5e9e 28
...
<<Output removed for brevity>>
...
Summary *192.168.0.1 192.168.0.7 0x80000001 687 0x22 0xb5a9 28
Summary 192.168.0.1 192.168.0.8 0x80000001 689 0x22 0xb9a3 28
Summary *192.168.0.2 192.168.0.7 0x80000001 687 0x22 0xb5a7 28
Summary 192.168.0.2 192.168.0.8 0x80000001 689 0x22 0xa5b7 28
Summary *192.168.0.3 192.168.0.7 0x80000001 687 0x22 0x97c6 28
Summary 192.168.0.3 192.168.0.8 0x80000001 689 0x22 0x9bc0 28
Summary *192.168.0.4 192.168.0.7 0x80000001 687 0x22 0x97c4 28
Summary 192.168.0.4 192.168.0.8 0x80000001 689 0x22 0x87d4 28
Summary *192.168.0.5 192.168.0.7 0x80000001 687 0x22 0x79e3 28
Summary 192.168.0.5 192.168.0.8 0x80000001 689 0x22 0x7ddd 28
Summary *192.168.0.6 192.168.0.7 0x80000001 687 0x22 0x79e1 28
Summary 192.168.0.6 192.168.0.8 0x80000001 689 0x22 0x69f1 28
Summary *192.168.0.7 192.168.0.7 0x80000001 687 0x22 0x5b01 28
Summary 192.168.0.7 192.168.0.8 0x80000001 689 0x22 0x5ffa 28
Summary *192.168.0.8 192.168.0.7 0x80000001 687 0x22 0x5bfe 28
Summary 192.168.0.8 192.168.0.8 0x80000001 689 0x22 0x4b0f 28
lab@vRouter-1:R7>Multi-Area OSPF And External Routes
The next thing we will look at is the behavior of external routes.
We’ll configure R1, R5, and R9 to advertise an external network into OSPF. This advertises an external network into OSPF from one router in each area.
- R1 will advertise 172.20.1.0/24
- R5 will advertise 172.20.0.0/24
- R9 will advertise 172.20.2.0/24
The third octet of each route represents the area number.
The configuration for R5 is shown below for reference. R1 and R9 are configured the same, using the relevant static route.
[edit]
lab@vRouter-1:R5# show routing-options
router-id 192.168.0.5;
static {
route 172.20.0.0/24 reject;
}
[edit]
lab@vRouter-1:R5# show policy-options
policy-statement exp-static {
term static {
from {
protocol static;
route-filter 172.20.0.0/16 longer;
}
then accept;
}
term final {
then reject;
}
}
[edit]
lab@vRouter-1:R5# show protocols ospf
area 0.0.0.0 {
interface lo0.5 {
passive;
}
interface lt-0/0/0.10 {
interface-type p2p;
}
interface lt-0/0/0.13 {
interface-type p2p;
}
interface lt-0/0/0.15 {
interface-type p2p;
}
}
export exp-static;
reference-bandwidth 100g;
[edit]
lab@vRouter-1:R5#External Route Verification
This time, we will validate the network from R6.
First, let’s look at the routes for the 172.20.x.x networks.
lab@vRouter-1:R6> show route 172.20/16
inet.0: 30 destinations, 30 routes (30 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
172.20.0.0/24 *[OSPF/150] 00:21:13, metric 0, tag 0
> to 172.16.56.1 via lt-0/0/0.14
172.20.1.0/24 *[OSPF/150] 00:21:08, metric 0, tag 0
to 172.16.46.1 via lt-0/0/0.12
> to 172.16.56.1 via lt-0/0/0.14
172.20.2.0/24 *[OSPF/150] 00:21:03, metric 0, tag 0
to 172.16.56.1 via lt-0/0/0.14
> to 172.16.68.2 via lt-0/0/0.17
lab@vRouter-1:R6>The routes are present, which is always a good start. Next, let’s look at the OSPF database.
lab@vRouter-1:R6> show ospf database
OSPF database, Area 0.0.0.0
Type ID Adv Rtr Seq Age Opt Cksum Len
Router 192.168.0.3 192.168.0.3 0x80000004 319 0x22 0x4b03 84
Router 192.168.0.4 192.168.0.4 0x80000005 321 0x22 0x959d 84
Router 192.168.0.5 192.168.0.5 0x80000004 1362 0x22 0x3864 108
Router *192.168.0.6 192.168.0.6 0x80000004 1366 0x22 0xb1bb 108
Router 192.168.0.7 192.168.0.7 0x80000003 1365 0x22 0xbae 84
Router 192.168.0.8 192.168.0.8 0x80000005 22 0x22 0x9b02 84
Summary 172.16.12.0 192.168.0.3 0x80000002 1336 0x22 0x7391 28
...
<<Output removed for brevity>>
...
Summary 192.168.0.10 192.168.0.7 0x80000001 1339 0x22 0x5106 28
Summary 192.168.0.10 192.168.0.8 0x80000002 220 0x22 0x3f17 28
ASBRSum 192.168.0.1 192.168.0.3 0x80000002 419 0x22 0xa9b9 28
ASBRSum 192.168.0.1 192.168.0.4 0x80000001 1335 0x22 0xafb2 28
ASBRSum 192.168.0.9 192.168.0.7 0x80000002 426 0x22 0x4116 28
ASBRSum 192.168.0.9 192.168.0.8 0x80000001 1338 0x22 0x470f 28
OSPF AS SCOPE link state database
Type ID Adv Rtr Seq Age Opt Cksum Len
Extern 172.20.0.0 192.168.0.5 0x80000001 1386 0x22 0x2162 36
Extern 172.20.1.0 192.168.0.1 0x80000001 1388 0x22 0x2e58 36
Extern 172.20.2.0 192.168.0.9 0x80000001 1391 0x22 0xf28a 36
lab@vRouter-1:R6>We now have a few extra types of LSAs in the OSPF database. We have external type-5 and ASBR Summary type-4 LSAs.
The externals represent the external networks that have been exported into OSPF. The ASBR Summaries allow R6 to know where the ASBR routers are in the other areas. The ASBR Summaries are generated by the ABR routers R3, R4, R7, and R8.
We can trace from R6’s loopback address to the ‘.1’ address of each of the external networks.
lab@vRouter-1:R6> traceroute 172.20.0.1 source 192.168.0.6
traceroute to 172.20.0.1 (172.20.0.1) from 192.168.0.6, 30 hops max, 52 byte packets
1 172.16.56.1 (172.16.56.1) 4.658 ms !N 4.008 ms !N 9.146 ms !N
lab@vRouter-1:R6> traceroute 172.20.1.1 source 192.168.0.6
traceroute to 172.20.1.1 (172.20.1.1) from 192.168.0.6, 30 hops max, 52 byte packets
1 172.16.56.1 (172.16.56.1) 5.140 ms 6.660 ms 3.258 ms
2 172.16.35.1 (172.16.35.1) 10.048 ms 6.974 ms 7.801 ms
3 172.16.13.1 (172.16.13.1) 5.109 ms !N 5.440 ms !N 3.960 ms !N
lab@vRouter-1:R6> traceroute 172.20.2.1 source 192.168.0.6
traceroute to 172.20.2.1 (172.20.2.1) from 192.168.0.6, 30 hops max, 52 byte packets
1 172.16.68.2 (172.16.68.2) 4.888 ms 4.273 ms 7.906 ms
2 172.16.180.2 (172.16.180.2) 3.536 ms 3.818 ms 3.136 ms
3 172.16.190.1 (172.16.190.1) 3.965 ms !N 3.542 ms !N 2.878 ms !N
lab@vRouter-1:R6>The paths are as follows:
- 172.20.0.1 – R6, R5.
- 172.20.1.1 – R6, R5, R3, R1.
- 172.20.2.1 – R6, R8, R10, R9.
Note: because R1, R5, and R9 had the static routes configured with a next-hop of reject, they generate an unreachable message for traffic destined for those networks. This is why we see the ‘!N’ in the last hop of the traceroute output.
Summary
In this post, we have looked at
- Advertising external routes into OSPF in each area.
- Basic multi-area OSPF configuration.