ASR9001 route policy source/destination prefix set questions

[andychen123456789]

Hi All,

We are very new to ASR 9001 XR platform, which we are bit confused route policy source/destination in if statement. We actually raised tech support, and they could not explain properly as well.

say, I have a eBGP session established in between router A, and B. on the router B. i have a prefix-set 1 to control the routes which i want to receive from router A, and i have another prefix-set 2 to control the routes which I want to send to router A.

in normal IOS way, we can either make prefix-list in/out, or use route map.

in XR, I understand that we need create route-policy, and because we want to control both direction routes on router B. we will have to make 23 route policy which for both IN and OUT direction.

Can I please ask in this situation, should we use if statement with source, or destination in prefix-set? or we use both IN/OUT direction policy route with IF statement for destination in prefix-set.

that is the part i am bit confused.

thank you if anyone could clarify with me.

Andy

[Tim.Yu]

Hi 

This is controlled via "in/out" when you attaching the policy on the peer. Below is one of the example:

neighbor 3.3.3.13
remote-as 6000
address-family ipv4 unicast
route-policy Inter_AS_in in
route-policy Inter_AS_out out
next-hop-self
soft-reconfiguration inbound always

Suggest you read this material.

https://supportforums.cisco.com/t5/service-providers-documents/asr9000-xr-understanding-and-using-rpl-route-policy-language/ta-p/3117050

[andychen123456789]

Hi ytpbit,

Yes, i understand it controls by IN/OUT in route policy,

my question was, in the route policy config, we use IF statement follow with 'source' or 'destination' as and then prefix-set to apply certain routes filter.

so, base on the case i post, on both in/out route policy, should i use source, or destination to filter both received and advertised routes?

e.g.

route-policy xyz-advertised-routes-filter

if destination/source in prefix-set-X then

pass

endif

route-policy received-routes-filter

if destination/source in prefix-set-Y then

pass

endif

Andy

[Tim.Yu]

Hi 

This does really confusing.

My understanding is:

Destination is the prefix/route you can see in the routing table

Source is the IP address of neighbour the prefix learnt.

So I suppose you use destination, not source in your case.

I implemented lots of cases of RPL, but seldom meet a case need source so far.

[thecrev · Accepted solution]

Hey,

I would use 'destination' in the routing policy for route advertisements to router A. That's what works for me. I've never tried using 'source' before.

I wish I could be more helpful on the routes that you want router B to accept from router A, but I usually just use a 'pass' policy for this. I suppose you can try 'destination' and 'source', to see what actually ends up getting populated in router B's table.