Solved address-family and VRF Lite

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Hi ITPro, wondering if someone can clear up my confusion over VRF Lite on IOS and this use of the "address-family" command when using eigrp with VRF Lite.

Below I've found an eigrp and ospf config example using VRFs and I notice that ospf isn't using the address-family command. To confirm, address-family is only used with eigrp or...?

router eigrp VRFS
 address-family ipv4 unicast vrf SALES autonomous-system 116
  network 192.168.16.0
  exit-address-family
 address-family ipv4 unicast vrf HR autonomous-system 132
  network 10.16.10.2 0.0.0.1
  exit-address-family

router ospf 1 vrf SALES
 network 192.168.16.0 0.0.0.255 area 0
 exit
router ospf 2 vrf HR
 network 10.16.10.2 0.0.0.1 area 0
 exit

@Adam-Tyler,

Didn't read the config as closely as I thought. I had to reread the output.
you're right, it does.

Here the difference between EIGRP and OSPF is the routing processing too.

With EIGRP, the address family with vrf allows the different router context without running separate EIGRP process.

With OSPF, without the address family, each VRF is treated as a different process separately...

I hate to say, I may be remembering this backward now.

@Adam-Tyler,

address-family is to provide for a separate routing context. This allows for a "virtualized" routing context in VRF lite (to hold two different routing) tables whereas normally you would only have a single one per router..

Hi Ronnie, thanks for getting back to me. How does the address-family use in eigrp compare with this approach in ospf? It appears these two ospf processes are running in different VRF contexts without the use of address-family? perhaps address-family is only used with eigrp?

router ospf 1 vrf SALES
 network 192.168.16.0 0.0.0.255 area 0
 exit
router ospf 2 vrf HR
 network 10.16.10.2 0.0.0.1 area 0
 exit

@Adam-Tyler,

You can do it with both. It just separates that EIGRP is being used with VRF and OSPF is running on the routing table outside of vrf.

Thanks Ronnie, just so I understand. This example is showing ospf "running on the routing table outside the vrf"?

router ospf 1 vrf SALES
 network 192.168.16.0 0.0.0.255 area 0
 exit
router ospf 2 vrf HR
 network 10.16.10.2 0.0.0.1 area 0
 exit

I was under in impression that the "vrf SALES" and "vrf HR" portions of these commands actually tied the ospf instance to the SALES and HR vrfs?

Regards,
Adam Tyler

@Adam-Tyler,

Didn't read the config as closely as I thought. I had to reread the output.
you're right, it does.

Here the difference between EIGRP and OSPF is the routing processing too.

With EIGRP, the address family with vrf allows the different router context without running separate EIGRP process.

With OSPF, without the address family, each VRF is treated as a different process separately...

I hate to say, I may be remembering this backward now.

https://virl.scsiraidguru.com/?page_id=1937

I did a VRF simulation. The code is in it.

@Ronnie-Wong Thanks Ronnie.. So using address family you can use the same eigrp AS number in different VRFs without conflicts. Got it.

Still a little confused as to why you would use address family with OSPF? Would the only benefit be the ability to use the same OSPF process number or...?

Regards,
Adam Tyler

@Adam-Tyler,

It would be for processing efficiency if anything that I can tell.