How does "match tag" works with "export map"

[Sherif Atef Ahmed Ismail]

Dears,

Although I have always used this command ... today is the first time I ask myself how it works

It seems I miss something

How does "match tag" works with "export map"

I am asking this cause "tag" doesnot appear except with static routes .... and export map should match on BGP routes not static routes

cause simply static routes may not be redistributed into BGP

----------------------

ip route vrf test 10.0.0.0 255.255.255.0 se1/0 tag 80

ip vrf test

rd 10283:11004

export map VPN-export

route-target export 10283:1001

route-target import 10283:1001

route-map VPN-export permit 10

match tag 80

set community no-advertise

set extcommunity rt 10283:214000

----------------------------

Many Thanks

BR

Sherif Ismail

[Vaibhava Varma]

Hi Sherif

You are correct that "match tag" will not work for routes learnt in the VRF via BGP process and being sent into the MP-iBGP cloud.

Route-Tag works for below cases:

1. Static Routes

2. Any Routes being redistributed into OSPF Process

3. Static Routes being redistributed into EIGRP Process

(In general route-tag does not works for ISIS also same as BGP)

So now if the config posted by you is applied then only the above mentioned routes can be exported to MP-iBGP. If PE-CE was BGP then definitely no route will be exported and only local static routes matching tag 80 will be exported.

However we can send both BGP as well local static routes based on "TAG" value by including one more permit statement under route-map which will permit all the remaining routes(BGP,Connected) which do not match TAG 80..

The export-map under VRF looks for all the routes present in the VRF and does a match on them based on the criteria provided. So the routes under VRF will be connected,static ( if any) and the PE-CE routing protocol used.

Hope this helps to provide some insight in your query.

Regards

Varma

[Sherif Atef Ahmed Ismail]

Thanks Varma for your reply

Actually with this setup, all routes will be exported cause of "route-target export" however static route with tag 80 will be exported with another tag due to "export-map"

My question is how export-map works

Seems to me, it works as below

1- First routes should be found in BGP ; thus static routes should be redistributed into BGP

2- Then route-map check routes in routing table not BGP table !!

OR
Another explanation that tag in static route is conveyed in BGP route (although it does not appear in "show ip bgpv4 vrf") then route-map checks routes in BGP table & not routing table

BR,

Sherif Ismail

[Vaibhava Varma]

Hi Sherif

Yes you are correct for the export of routes under the VRF with respect to the export-map and "route-target export".I overlooked the export behaviour with being same as import.

In my understanding the export-map will match for the routes present in the Local VRF Routing Table against the match conditions provided.If we need to match based on TAG then there should be a local static route or an OSPF External ROute or an EIGRP External Route with the corresponding tag .Static Route when redistributed under BGP looses the TAG value and thats why its not seen under the "show ip bgp vpnv4 vrf" output.

Regards

Varma

[Sherif Atef Ahmed Ismail]

A friend of mine told me an explanation ... and seems to be v.logic

during redistribution of static routes into BGP, route-map set of export-map is applied

Thx Varma for your assistance