Re: BGP Readvertise routes

Rick Morris · ‎07-10-2009

What is done to readvertise routes learned bia BGP.

For instance, I have 2 separate networks 10.1.1.0 and 10.2.2.0.

In the topology

CE Router 10.1.1.0 --- PE RouterA --- Pe RouterB --- CE Router 10.2.2.0

If CE Router 10.1.1.0 advertises its routes to PE Router A and CE Router 10.2.2.0 advertises its routes to PE Router B, how to the 2 PE routers send those routes to each other?

They are currently running BGP between the 2 PE routers. You can see in the sh ip bgp neighbor of each side that the routes are seen as iBGP but neither side can ping.

see previous thread:

http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&type=Subscriptions&loc=.2cd411e5/7&forum=Network%20Infrastructure&topic=WAN%2C%20Routing%20and%20Switching

I think this may simplify my last thread a little.

Giuseppe Larosa · ‎07-10-2009

Hello Rick,

>> If CE Router 10.1.1.0 advertises its routes to PE Router A and CE Router 10.2.2.0 advertises its routes to PE Router B, how to the 2 PE routers send those routes to each other?

by using an iBGP session between them (PE1-PE2) under the condition that what you call CE1 and CE2 have true eBGP sessions with PE1 and PE2.

I mean:

CE1 AS number x

CE2 AS number y

PE1 and PE2 AS number Z

Edit:

I think it would be better to go on that thread where Jon has followed you and where you have provided full details

Hope to help

Giuseppe

Rick Morris · ‎07-10-2009

CE1 AS-1000

CE2 AS-1000

PE1 AS-209

PE2 AS-209

eBGP between ce and pe and iBGP between pe's

here is the specific example of what I am talking about:

CARRIER-A#sh ip bgp sum

BGP router identifier 210.1.1.1, local AS number 209

BGP table version is 31, main routing table version 31

2 network entries using 264 bytes of memory

3 path entries using 156 bytes of memory

5/2 BGP path/bestpath attribute entries using 740 bytes of memory

2 BGP AS-PATH entries using 48 bytes of memory

0 BGP route-map cache entries using 0 bytes of memory

0 BGP filter-list cache entries using 0 bytes of memory

Bitfield cache entries: current 1 (at peak 2) using 32 bytes of memory

BGP using 1240 total bytes of memory

BGP activity 29/27 prefixes, 44/41 paths, scan interval 60 secs

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd

123.2.2.2 4 209 2834 2813 31 0 0 1d23h 1

208.10.10.1 4 1000 11544 11431 31 0 0 1d01h 1

208.10.10.2 4 1000 4235 4198 31 0 0 1d23h 1

CARRIER-A#sh ip bgp neigh 123.2.2.2 adv

BGP table version is 31, local router ID is 210.1.1.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

*> 63.10.10.0/24 208.10.10.1 0 100 0 1000 i

Total number of prefixes 1

CARRIER-A#sh ip bgp neigh 123.2.2.2 ro

BGP table version is 31, local router ID is 210.1.1.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

* i63.20.20.0/24 123.2.2.2 0 100 0 1000 i

Total number of prefixes 1

CARRIER-B#sh ip bgp sum

BGP router identifier 210.2.2.1, local AS number 209

BGP table version is 31, main routing table version 31

2 network entries using 240 bytes of memory

3 path entries using 156 bytes of memory

3/2 BGP path/bestpath attribute entries using 372 bytes of memory

1 BGP AS-PATH entries using 24 bytes of memory

0 BGP route-map cache entries using 0 bytes of memory

0 BGP filter-list cache entries using 0 bytes of memory

Bitfield cache entries: current 1 (at peak 2) using 32 bytes of memory

BGP using 824 total bytes of memory

BGP activity 20/18 prefixes, 23/20 paths, scan interval 60 secs

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd

123.1.1.2 4 209 2814 2835 31 0 0 1d23h 1

208.20.20.1 4 1000 2953 2954 31 0 0 1d23h 1

208.20.20.2 4 1000 2951 2955 31 0 0 1d23h 1

CARRIER-B#sh ip bgp neigh 123.1.1.2 adv

BGP table version is 31, local router ID is 210.2.2.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

*> 63.20.20.0/24 208.20.20.1 0 100 0 1000 i

Total number of prefixes 1

CARRIER-B#sh ip bgp neigh 123.1.1.2 ro

BGP table version is 31, local router ID is 210.2.2.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

* i63.10.10.0/24 123.1.1.2 0 100 0 1000 i

Total number of prefixes 1

however I cannot ping either sides network.

Giuseppe Larosa · ‎07-10-2009

Hello Rick,

see the other thread I think I've found the issue.

Hope to help

Giuseppe

Mohamed Sobair · ‎07-10-2009

Hi Rick,

lets name it CE1 , CE2 , PE1 , PE2:

1- CE1 advertises Network 10.1.1.0 to PE1 via Static, RIP, Eigrp , OSPF or BGP.

2- PE1 has Network 10.1.1.0 in its VRF table.

3- PE1 advertises Network 10.1.1.0 to PE2 as VPNv4 Network through its normal IBGP session.

4- PE2 imports Network 10.1.1.0 into the correct VRF table for CE2.

5- PE2 advertises Network 10.1.1.0 to CE2 through normal BGP - IGP redistribution.

6- CE2 gets Network 10.1.1.0 in its routing table.

7- Oppsite is correct for Network 10.2.2.0

Hope to help

Mohamed