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Frequent Contributor

BGP Experts | ur kind support

Hi Experts

i have a public as along with public class C form RIPE ,currently i m multihoming to 2 ISPs , but from the global Internet i m appear to be connected only via ISP1 even though on my bgp router i have seen the route (default route) from ISP2 , a.k.a i have bgp peering up  with isp-1 and isp-2

once the link towards isp-1 down i disappeared from the Internet,

where the problem is?is it from my side our from isp-2 side

pls help

jamil

10 REPLIES 10
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Advisor

Re: BGP Experts | ur kind support

Jamil,

Can you post "sh ip bgp summary" and "sh ip (isp2 address) neighbor advertised"?

John

Sent from Cisco Technical Support iPhone App

HTH, John *** Please rate all useful posts ***
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Frequent Contributor

BGP Experts | ur kind support

Hi John

  • sh ip bgp summary shows i have bgp peering with both ISPs
  • sh ip bgp neigh X.X.X.X advertised-routes : shows my Public class C address advertised to them with the sign *>
  • sh ip bgp neigh X.X.X.X routes : shows the default routes coming from both ISPs
  • also form ISP-2 side he receives my route

forgive me jhon for X.X.X.X , i couldn't disclose my address space

jamil

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Rising star

BGP Experts | ur kind support

hi ibrahim,

how are your routers cnnected? Are they connected via iBGP with each other. Do you have HSRP on your routers? What is your network setup .can you please show you network diagram here? Do you have an IGP? is the default route redistibuted into IGP etc?

Regards, Kishore

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BGP Experts | ur kind support

you need to confirm with ISP2 that they are allowing your AS number and your public IP range to be advertised through their network

Highlighted
Frequent Contributor

BGP Experts | ur kind support

Hi

thanks for ur reply

how can they verify if my as and my public IP Range to be advertised via their network?

thanks

jamil

Highlighted
Rising star

BGP Experts | ur kind support

hi jamil,

if you want to knw whether your ISP is advertising to upstream or not. you can always check if your ISP's upstream has a route server or a looking glass. you can put your ip address in and it should show you. Alternatively, you can ask your ISP to perhaps show that they are adversiting on their border router etc.

HTH

Kishore

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Collaborator

Re: BGP Experts | ur kind support

Hi Jamil,

Use any BGP looking-glass (i.e. http://lg.he.net) and show the results to your ISP2. They may be peering with you but they may not be advertising your prefix. As they are your ISP, you can share in detail to them your configuration whether your advertisement to them is correct.

Dandy

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Rising star

Re: BGP Experts | ur kind support

I agree with marwanshawi. I'm assuming you have talked to both ISPs since you have a peering relationship with both of them. Do you have a Provider-Independent Network or a Provider-Advertised Network that you are advertising through BGP? Also, I would obviously call them up and ask why it appears as if they are not advertising your prefix.

As long as when you do 'show ip bgp summary' and you have a peering relationship in the correct state, and you have verified that you are indeed advertising successfully your network to ISP2, then it sounds like a provider problem.

Highlighted
Frequent Contributor

BGP Experts | ur kind support

Hi Guys

Thank you all for ur great` reply

strange thing happend , the big ISP in UK who provide ISP service to my ISP which i have connected didnt annouce my prefix , so now its okay

thanks

ibrahim

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Frequent Contributor

BGP Experts | ur kind support

hi dandy

i have noted that http://lg.he.net isn't up to to date in term of route propogation

thanks

jamil