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Community Member

BGP - Changing a preferred route

Guys,

How do I make a route be preferred by one AS over another.

My issues is as follows:

I need to adjust the routing here so that all traffic to the 208.203.222.64 network goes out over the T3 AS 65203. As you can see from the Tracert its now going out over:

C:\Users\rodonoh1>tracert 208.203.222.66

Tracing route to GMACCM [208.203.222.66]

over a maximum of 30 hops:

1 2 ms 1 ms 1 ms 172.17.5.2

2 1 ms 1 ms 1 ms 172.17.2.19

3 151 ms 32 ms * 172.17.0.2

4 * * * Request timed out.

5 180 ms * 318 ms 192.168.0.45

6 305 ms 119 ms 119 ms GMACCM [208.203.222.66]

But I want it to go out over the path to 192.168.0.253 as the next hop.

How can I set this route a higher priority as in the case with say the proxy.gmaccm.com ip

Clo-IR-7206a#sh ip route 192.168.176.132

Routing entry for 192.168.0.0/16, supernet

Known via "bgp 65203", distance 20, metric 0

Tag 65100, type external

Last update from 192.168.0.253 7w0d ago

Routing Descriptor Blocks:

* 192.168.0.253, from 192.168.0.253, 7w0d ago

Route metric is 0, traffic share count is 1

AS Hops 1

The current sh ip bgp :

* i208.203.222.64/27

172.17.2.230 0 100 0 19855 65110 i

*>i 172.17.2.230 0 100 0 19855 65110 i

* 192.168.0.253 0 65100 19855 65110 i

Network Next Hop Metric LocPrf Weight Path

How do i change it so it goes out over the 192.168.0.253 route and that AS

1 ACCEPTED SOLUTION

Accepted Solutions
Community Member

Re: BGP - Changing a preferred route

you need to run

"neighbor x.x.x.x soft-reconfiguration nbound" on config-router prompt.

Cheers,

Rajesh

9 REPLIES
Community Member

Re: BGP - Changing a preferred route

Hi,

You can set higher local preferene for routes learned from preferrred provider.

HTH.

Cheers,

Rajesh

Community Member

Re: BGP - Changing a preferred route

Thanks but how do i do that in this instance?

What part of the current config should I provide you to explain my issue better?

Re: BGP - Changing a preferred route

For 192.168.0.253 to be preferred as the next-hop, you need to increase the local preference for routes learnt from this neighbor.

access-list 15 208.203.222.64 0.0.0.32

route-map t3 permit 10

match ip address 10

set local-preference 200

route-map t3 permit 20

router bgp xxxx

neighbor 192.168.0.253 route-map t3 in

Community Member

Re: BGP - Changing a preferred route

thats brilliant.

does this change take effect straight away or do i need to make a change for the routes to update? do a clear ip * ???

Thanks again

Community Member

Re: BGP - Changing a preferred route

you need to run

"neighbor x.x.x.x soft-reconfiguration nbound" on config-router prompt.

Cheers,

Rajesh

Community Member

Re: BGP - Changing a preferred route

Thanks a millon. this worked.

Cisco Employee

Re: BGP - Changing a preferred route

Rajesh,

Just as side note, "neighbor soft-reconfiguration" is not required if the BGP Soft Reset has been implemented. BGP Soft Reset is somewhat superior as it provides the same benefits as soft-reconfiguration (dinamically reprocessing the inbound updates via a clear ip bgp * soft in) without consuming the additional memory. BGP Soft Reset has been in the IOS for long time.

Please refer to the following document for more information on BGP Soft Reset.

http://www.cisco.com/en/US/products/ps6599/products_data_sheet09186a0080087b3a.html

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Community Member

Re: BGP - Changing a preferred route

Hi,

Noted , It's valid point, Basically both the BGP peers must support route refresh feature.

if it supports it will ask the peer to send complete route update and apply policies on updates and subesequestly pushed into route table.

Cheers,

Rajesh

Community Member

Re: BGP - Changing a preferred route

guys thanks for the help on this.I'm tying to get a good understanding of BGP. Do you know any good texts or simulators\examples i could look at to get some experince with it.

Thanks again,

Rob.

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