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
Can you post "sh ip bgp summary" and "sh ip (isp2 address) neighbor advertised"?
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forgive me jhon for X.X.X.X , i couldn't disclose my address space
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?
you need to confirm with ISP2 that they are allowing your AS number and your public IP range to be advertised through their network
thanks for ur reply
how can they verify if my as and my public IP Range to be advertised via their network?
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.
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.
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.
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