CCIE SP – OSPF

OSPF – Unicast, Multicast Reachability.

Configuration:
RP/0/0/CPU0:XRV-01#sh run router ospf
Wed Jul 11 00:14:28.130 UTC
router ospf 1
area 0
interface Loopback0
!
interface GigabitEthernet0/0/0/0.12
!
interface GigabitEthernet0/0/0/0.111
!
interface GigabitEthernet0/0/0/0.211
!
RP/0/0/CPU0:XRV-01#sh run router ospfv3
Wed Jul 11 00:14:37.150 UTC
router ospfv3 1
area 0
interface Loopback0
!
interface GigabitEthernet0/0/0/0.12
!
interface GigabitEthernet0/0/0/0.111
!
interface GigabitEthernet0/0/0/0.211
!

Note: Even though we have the same ospf process for OSPFv2 & OSPFv3 with process #1, Router see it independently to each other because they’re advertising different address-family.

Verification IOS:
IPV4 #show ip int brief || IPV6 #show ipv6 interface brief
IPV4 #show ip ospf neighbor || IPV6 #show ipv6 ospf neighbor

For XR
All of the config. for routing protocols is gonna go under “Global Process”, So once we establish link connectivity on link level, then we have v4/v6 addressing configured next step is to go onto the global process and enable the protocol interface link level.

Verification XR:
#show ospf neighbors
#show ospf interface

Note: We can’t see any logging message in XR that the ospf adjacency went up because by default it’s using lower logging message. We need to set it to “debugging”.
71120818coreospfie
Once we configure all the core routers to ospf, all routers will have the same database. The difference will be just the router id.

R1#sh ip ospf database

OSPF Router with ID (1.1.1.1) (Process ID 1)

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count
1.1.1.1 1.1.1.1 1807 0x80000019 0x000A56 4
1.1.1.2 1.1.1.2 930 0x8000000B 0x0072C3 5
1.1.1.4 1.1.1.4 962 0x8000000B 0x008CC7 4
2.1.1.1 2.1.1.1 1163 0x80000019 0x003403 4
2.1.1.2 2.1.1.2 1014 0x80000020 0x002D5F 6
2.1.1.3 2.1.1.3 1252 0x8000000C 0x0045CC 5

Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum
10.1.2.1 1.1.1.1 1037 0x80000013 0x0011FB
10.1.11.2 1.1.1.1 1299 0x80000013 0x00A062
10.1.12.1 2.1.1.2 1014 0x80000013 0x009E61
10.2.3.2 1.1.1.4 962 0x80000008 0x0012FC
10.2.11.1 2.1.1.1 1163 0x80000016 0x009964
10.2.12.1 2.1.1.2 1265 0x80000016 0x009664
10.3.12.1 2.1.1.2 1014 0x8000000C 0x00B24F
10.3.13.1 2.1.1.3 1252 0x80000008 0x00B74B
10.11.12.1 2.1.1.1 920 0x80000013 0x0033C2
10.12.13.1 2.1.1.2 1782 0x80000008 0x0044B7

RP/0/0/CPU0:XRV-01#sh ospf database
Wed Jul 11 00:23:13.814 UTC

OSPF Router with ID (2.1.1.1) (Process ID 1)

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count
1.1.1.1 1.1.1.1 1775 0x80000019 0x000a56 4
1.1.1.2 1.1.1.2 897 0x8000000b 0x0072c3 5
1.1.1.4 1.1.1.4 929 0x8000000b 0x008cc7 4
2.1.1.1 2.1.1.1 1129 0x80000019 0x003403 4
2.1.1.2 2.1.1.2 981 0x80000020 0x002d5f 6
2.1.1.3 2.1.1.3 1219 0x8000000c 0x0045cc 5

The final end result is to check the router routing table, If router do actually know the loopbacks of the devices, Transit interface between device or do router have IP reachability between neighbors.

Ospf version 2 & 3 forming adjacencies
Before we got to any upper layer protocols we want to make sure the core connectivity is there. Both for OSPFv2 and v3 or for IS-IS.

Interms of IPv6 connectivity, Since we are not using ipv6 as the source and destination of the MLS tunnel. The only thing that ipv6 connectivity would affect is if we were doing internet connectivity for IPv6.

If we want to tunnel IPv6 over MPLS we don’t need ipv6 enabled on the core, We can run either the “6PE or 6VPE” Feature in order to tunnel IPv6 over IPv4 based label core.

For the same type of matching route, OSPFv3 is more preffered that OSPFv2.

Note: You cannot run ospfv3 with OSPFv2, Even redistribtion (Selective). XR os will not advertise v3 ipv4 address family to v2.

OSPFv3 is not backwards compatible with V2, you have to be running same version of the protocol between the two neighbors and one of the main reason is that it use separate transport.

So for IPv4 address-family advertised in OSPFv3 it uses IPv6 for transport. We need to enable ipv6 on interface in order to run OSPFv3 IPv4.

Configuration to enable ipv6: (int)ipv6 enable
This command will be use to generate link local address that is based on EUI-64 format (mac-address).

Not all version support redistribution of OSPFv3. Means if the question ask you to run OSPF to PE-CE routing protocol and If your version doesn’t support v3 redistribution, it mean you need to run OSPFv2.

Note: You can redistribute ipv4 v2 to OSPFv3 but not the other way around.

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