BGP Changing question

binargs

Hi all,
I am not there in the CCNP level yet, currently doing CCNA: Voice

but i have a project coming up and basically i need to reconfig the router to a new isp and form a neighbor with the new isp router with bgp. i read the chapters on bgp in the ccnp route book and i understood about 70% of it. the only route the isp is advertising to us is the default route and we are advertising a few route back to them. besides the basics, is there anything else i need to worry about?

router bgp asn#
neighbor ipaddress remote-as asnnum
version 4 (this is a really old router and i am pressing them to upgrade it)
neighbor ipaddress soft-reconfiguration inbound
neighbor ipaddress distribute-list 110 out
network ipsiwanttoadvertise

wave

Looks right to me based on what you've outlined. Check that auto-summarization is disabled because it was ON by default in earlier IOS versions.

When you advertise networks make sure an explicit route exists in the routing table and be sure to specify the mask like this: 200.200.200.0 mask 255.255.255.0

NetworkVeteran

binargs wrote: »

Hi all,
I am not there in the CCNP level yet, currently doing CCNA: Voice

but i have a project coming up and basically i need to reconfig the router to a new isp and form a neighbor with the new isp router with bgp. i read the chapters on bgp in the ccnp route book and i understood about 70% of it. the only route the isp is advertising to us is the default route and we are advertising a few route back to them. besides the basics, is there anything else i need to worry about?

router bgp asn#
neighbor ipaddress remote-as asnnum
version 4 (this is a really old router and i am pressing them to upgrade it)
neighbor ipaddress soft-reconfiguration inbound
neighbor ipaddress distribute-list 110 out
network ipsiwanttoadvertise

If all goes well, BGP is simple to configure and that should do it. My biggest concern is that, if you only grasp 70% of the already-light coverage of BGP in the CCNP Route book, you may not know it well enough to accurately configure the details and troubleshoot if there be problems. Suppose the neighbor is stuck in the Active state. What would you do?

If I had an engineer in a similar boat, I'd make the following suggestions--

1) Lab the scenario ahead of time to identify any complications and figure out how to resolve them when not under-the-gun. You can do this using either real hardware or using a simulator such as GNS3.
2) Invest more time improving your understanding of BGP.
3) Have a BGP-expert watching or on-call.

If you have a long roll-out window, say "all Saturday", then this is less of a concern.

binargs

hi all, thanks for the replies.

if the bgp is stuck at the active state i will try to figure out why it did, but there doesn't seem alot can go wrong in establishing bgp neighbors, password mismatch, is the neighbor ip and asn configured on the other side, etc. if necessary i can do a debug ip bgp and see is the open messages are sent or not. i understood 70% because the bgp chapter was the only one that i read out of the book, so a couple of things, like distribution lists, i didn't had a clue about due to the skipping ahead.

but you are completely right, i should try this out on the gns. currently the change is scheduled with a isp engineer on a night due to people using the network 24/7. the plan b right now is that don't save anything. if things don't work out, reboot router. but then again, it is a 10+ year old router, running ios show ver = 12.0(5)T1. i am pressing hard for them to get a new router because i am not sure the new ios will even run on that router, and as right now it's a really serious security risk.

NetworkVeteran

binargs wrote: »

if the bgp is stuck at the active state i will try to figure out why it did, but there doesn't seem alot can go wrong in establishing bgp neighbors, password mismatch, is the neighbor ip and asn configured on the other side, etc. if necessary i can do a debug ip bgp and see is the open messages are sent or not. i understood 70% because the bgp chapter was the only one that i read out of the book, so a couple of things, like distribution lists, i didn't had a clue about due to the skipping ahead.

OIC. You are not in such bad shape, then.

i should try this out on the gns.

Good luck!