BGP Redistribution question

Tue Aug 10 15:03:06 UTC 2004

Hello.

Redistribute ospf xx subnets has some unusual behavior
compared to other redistribution mechanisms.  Instead of
dumping everything from ospf into the other routing
protocol, it only does a subset of routes.  (If I remember
right, only "internal" routes.)

I think the command you probably want is...

Redistribute ospf 123 match internal external 1	 external 2

Also, if you have nssa's, you may have to tack nssa-external
on the end of that.

Good luck,
Ejay

P.s. Unidrectional redistribution good.  Bidirectional
redistribution Bad

> -----Original Message-----
> From: owner-nanog at merit.edu [mailto:owner-nanog at merit.edu]
On 
> Behalf Of D Train
> Sent: Thursday, August 05, 2004 10:09 AM
> To: nanog at nanog.org
> Subject: BGP Redistribution question
> 
> 
> While looking into a routing issue, I found that one
> of my routers wasn't passing one of my static routes,
> being redist into ospf into bgp, and not sure as to
> why. It has been a while since I have worked with BGP,
> so I am a little rusty. The solution was for me to add
> the following BGP network statement... network
> 10.86.8.0 mask 255.255.248.0. If statics are being
> redist info ospf, and ospf is basically being redist
> into bgp, why did I have to have the network
> statement. Why didn't it put it into BGP and pass it
> along?
> 
> Here is the scenario:
> Router A:
> ip route 10.86.8.0 255.255.248.0 10.86.138.14
> 
> ATL--CR6513A#ping 10.86.138.14
> success rate is 100 percent (5/5), round-trip
> min/avg/max = 1/1/4 ms
> 
> ATL -CR6513A#sh ip route 10.86.8.0 
> Routing entry for 10.86.8.0/21
> Known via "static", distance 1, metric 0
> Redistributing via ospf 1
> Advertised by ospf 1 subnets
> bgp 2
> Routing Descriptor Blocks:
> * 10.86.138.14
> Route metric is 0, traffic share count is 1
> 
> ATL-CR6513A#sh ip ospf data ext 10.86.8.0
> OSPF Router with ID (10.86.194.5) (Process ID 1)
> Type-5 AS External Link States
> Routing Bit Set on this LSA
> LS age: 898
> Options: (No TOS-capability, DC)
> LS Type: AS External Link
> Link State ID: 10.86.8.0 (External Network Number )
> Advertising Router: 10.86.194.2
> LS Seq Number: 80000D87
> Checksum: 0x3D49
> Length: 36
> Network Mask: /21
> Metric Type: 2 (Larger than any link state path)
> TOS: 0 
> Metric: 20 
> Forward Address: 0.0.0.0
> External Route Tag: 0
> LS age: 554
> Options: (No TOS-capability, DC)
> LS Type: AS External Link
> Link State ID: 10.86.8.0 (External Network Number )
> Advertising Router: 10.86.194.5
> LS Seq Number: 80000D87
> Checksum: 0x2B58
> Length: 36
> Network Mask: /21
> Metric Type: 2 (Larger than any link state path)
> TOS: 0 
> Metric: 20 
> Forward Address: 0.0.0.0
> External Route Tag: 0
> 
> ATL-CR6513A#sh ip bgp 10.86.8.0
> BGP routing table entry for 10.86.0.0/16, version
> 1078065
> Paths: (2 available, best #2, table
> Default-IP-Routing-Table)
> Multipath: eBGP
> Advertised to non peer-group peers:
> 10.1.2.9 
> 1, (aggregated by 1 10.1.254.253)
> 10.1.2.9 from 10.1.2.9 (10.1.254.253)
> Origin IGP, metric 0, localpref 100, valid, external,
> atomic-aggregate, multipath
> 1, (aggregated by 1 10.1.254.252)
> 10.1.2.1 from 10.1.2.1 (10.1.254.252)
> Origin IGP, metric 0, localpref 100, valid, external,
> atomic-aggregate, multipath, best
> 
> router ospf 1
> redistribute static subnets
> router bgp 2
> no synchronization
> network x.x.x.x
> network y.y.y.y
> network 10.86.8.0 mask 255.255.248.0 ***had to be
> added for this to work, but wasn't present before
> hand***
> redistribute connected route-map OSPF-Links
> redistribute ospf 1 route-map WW-OSPF-Routes
> neighbor 10.1.2.1 remote-as 1
> neighbor 10.1.2.1 advertisement-interval 1
> neighbor 10.1.2.9 remote-as 1
> neighbor 10.1.2.9 advertisement-interval 1
> maximum-paths 2
> no auto-summary
> 
> route-map WW-OSPF-Routes permit 10
> set metric-type internal
> 
> This is I was seeing on my Upstream Core router:
> ATL -CR12406A#sh ip route 10.86.8.0
> Routing entry for 10.86.0.0/16
> Known via "bgp 1", distance 200, metric 0, type
> locally generated
> Routing Descriptor Blocks:
> * directly connected, via Null0
> Route metric is 0, traffic share count is 1
> AS Hops 0, BGP network version 
>  
> This is what I was seeing after I add the network
> statement:
> 
> GAATL-WW1-CR12406A#sh ip bgp 10.86.8.0
> 
> BGP routing table entry for 10.86.8.0/21, version
> 2210556
> 
> Paths: (2 available, best #2, Advertisements
> suppressed by an aggregate.)
> 
> Multipath: eBGP iBGP
> Not advertised to any peer
> 2
> 10.1.2.2 from 10.1.2.2 (10.86.194.5)
> Origin IGP, metric 0, localpref 100, valid, external,
> multipath
> 2
> 10.1.2.6 from 10.1.2.6 (10.86.194.2)
> Origin IGP, metric 0, localpref 100, valid, external,
> multipath, best
> 
>  
> 
> 
> 
> 
> 		
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