BGP route question

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Aug 27th, 2008
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Hello,


In the following command:


Routing entry for xx.xxx.xx.0/24

Known via "bgp 11111", distance 20, metric 0

Tag 64561, type external

Advertised by bgp 111xx (self originated)

Last update from xxx.xxx.xxx.xxx 07:47:41 ago

Routing Descriptor Blocks:

* xxx.xxx.xxx.xxx, from xxx.xxx.xxx.xxx, 07:47:41 ago

Route metric is 0, traffic share count is 1

AS Hops 1

Route tag 64561


Can anyone tell me what (self originated) means, I would think it should not say that, considered it is learned from an EBGP peer, I edited out the IP addresses..

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Edison Ortiz Wed, 08/27/2008 - 18:08
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It means you have a network statement or redistribution process under BGP which is including that route.


Here is a sample


R1#sh ip route 99.99.99.5

Routing entry for 99.99.99.5/32

Known via "bgp 1", distance 20, metric 0

Tag 5, type external

Last update from 155.1.0.5 00:00:52 ago

Routing Descriptor Blocks:

* 155.1.0.5, from 155.1.0.5, 00:00:52 ago

Route metric is 0, traffic share count is 1

AS Hops 1

Route tag 5


!

!

!


R1(config)#router bgp 1

R1(config-router)#net 99.99.99.5 mask 255.255.255.255

R1(config-router)#end

R1#sh ip route 99.99.99.5

!

!

!

Routing entry for 99.99.99.5/32

Known via "bgp 1", distance 20, metric 0

Tag 5, type external

Advertised by bgp 1 (self originated)

Last update from 155.1.0.5 00:01:18 ago

Routing Descriptor Blocks:

* 155.1.0.5, from 155.1.0.5, 00:01:18 ago

Route metric is 0, traffic share count is 1

AS Hops 1

Route tag 5


HTH,


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Jasonch518_2 Wed, 08/27/2008 - 18:17
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Thanks,


I actually thought of that, and yes I do have a network statement, for an aggregate block that includes this /24, but reason I rules it out is, I have an aggregate for a different IP block and that IP block shows up normal, not self originated, so is there anything that would make that other IP block not show as self originated, even though there commands are there to do it, but this one does, and it has the same setup, and same aggregate network statement, different /19's though.


Thanks.

Edison Ortiz Wed, 08/27/2008 - 19:37
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Was the other network also learned via eBGP?


If so, I'm not sure why isn't showing as self-originated which is the expected behavior as you saw in my example.


Posting config and show ip bgp / show ip route output will help.


__


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Jasonch518_2 Wed, 08/27/2008 - 20:17
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I appreciate the help, here is the information you were looking for, I replaced the IP addresses with private ones, but kept the same netmask structure of the actual IP. Also, these IP blocks are learned from a router that is dual homed to my network, so I have 2 edge routers, each peering with the 2 private AS's, learning the class C from each. The primary edge router, the one with the self originate is the one where i included the bgp configuration, its pretty much the same on the other router, but the network statements are on the primary, so I included them, as well as 2 Null routes that are in my table, for the aggregate being sent upstream.


Routing entry for 10.168.64.0/24

Known via "bgp 11111", distance 20, metric 0

Tag 64561, type external

Advertised by bgp 11111 (self originated)

Last update from ZZZ.ZZZ.ZZZ.ZZZ 10:17:14 ago

Routing Descriptor Blocks:

* ZZZ.ZZZ.ZZZ.ZZZ, from ZZZ.ZZZ.ZZZ.ZZZ, 10:17:14 ago

Route metric is 0, traffic share count is 1

AS Hops 1

Route tag 64561


Routing entry for 172.16.112.0/24

Known via "bgp 11111", distance 20, metric 0

Tag 64558, type external

Last update from YYY.YYY.YYY.YYY 1w2d ago

Routing Descriptor Blocks:

* YYY.YYY.YYY.YYY, from YYY.YYY.YYY.YYY, 1w2d ago

Route metric is 0, traffic share count is 1

AS Hops 1

Route tag 64558


router bgp 11111

no synchronization

bgp log-neighbor-changes

bgp dampening


network 10.168.64.0 mask 255.255.224.0

network 172.16.96.0 mask 255.255.224.0

redistribute static

no auto-summary



BGP routing table entry for 10.168.88.0/24, version 93308146

Paths: (2 available, best #1, table Default-IP-Routing-Table)

Advertised to update-groups:

1 6

64561, (received & used)

ZZZ.ZZZ.ZZZ.ZZZ from ZZZ.ZZZ.ZZZ.ZZZ (ZZZ.ZZZ.ZZZ.ZZZ)

Origin IGP, metric 0, localpref 100, valid, external, best

64561, (received & used)

ZZZ.ZZZ.ZZZ.ZZZ (metric 2) from ZZZ.ZZZ.ZZZ.ZZ (ZZZ.ZZZ.ZZZ.ZZ)

Origin IGP, metric 0, localpref 100, valid, internal


BGP routing table entry for 172.16.112.0/24, version 91730099

Paths: (2 available, best #2, table Default-IP-Routing-Table)

Advertised to update-groups:

1 6

64558, (received & used)

YYY.YYY.YYY.YY (metric 2) from YYY.YYY.YYY.YY (YYY.YYY.YYY.YY)

Origin IGP, metric 0, localpref 100, valid, internal

64558, (received & used)

YYY.YYY.YYY.YYY from YYY.YYY.YYY.YYY (YY.YYY.YY.YYY)

Origin IGP, metric 0, localpref 100, valid, external, best




ip route 10.168.64.0 255.255.224.0 Null0 200 name BGP-Summary-Route



ip route 172.16.96.0 255.255.224.0 Null0


















Edison Ortiz Thu, 08/28/2008 - 09:47
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There is something missing:


Routing entry for 10.168.64.0/24


It's not the same as:


network 10.168.64.0 mask 255.255.224.0


Please verify you aren't bringing that route into BGP via other means.


and this route:


Routing entry for 172.16.112.0/24


is not the same as:


network 172.16.96.0 mask 255.255.224.0


Keep in mind, in order to bring a route into BGP via network statement, you must match the route and subnet as its seen in the routing table.


It's not like an IGP network statement where you can summarize an entry and capture multiple subnets.



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Jasonch518_2 Thu, 08/28/2008 - 15:09
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Ah, so the network statement will not catch it, unless it was an aggregate network statement correct?


I will keep looking, thanks for the help so far.

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