A1) an ISP might have a peering contract with another ISP stating something about announced routes. As your IP network is not belonging to your ISP this might have been filtered (BGP update not accepted) by upstream ISPs.
A2) There is a command which says "remove-private-as" when sending BGP updates to a peer. So it is rather simple with a Cisco router, actually one line of configuration.
A3) This is more tricky than it seems at the first look. One answer could be: you can not. In fact every AUTONOMOUS system can influence where they think the best (for them) return path is. All you can do is to give "hints" to the internet. The most reliable situation can be achieved in case your ISP1 and ISP2 are directly peering. Use AS path prepending (longer path is worse) to control return traffic.
A4) Configuring AS path prepending ("repeated AS") is configured like this:
router bgp 65000
neighbor 126.96.36.199 remote-as 65500
neighbor 188.8.131.52 route-map ASprep out
route-map ASprep permit 10
match ip address prefix-list 123
set as-path-prepend 65000 65000 65000 65000
ip prefix-list 123 seq 5 permit 195.X.X.X/24
This way you will insert your AS number 4 times (which should be sufficient for all customers).
Thanks, it was kind of you to answer my queries. Can you please tell me any specific reason why an ISP should block some networks being advertised by its down stream. Since if every ISP is selective in the blocks that it would accpet from down streams, then we might not have a fully reachable internet. And more over, each ISP would then have to contact thier respective UP Streams to update there filters and to what extent will this happen?... Awaiting a response. Please reply. Thanks.
good question ... and valid point. Still it depends on the peering contract your ISP has. It is not inevitably so, that he is transit AS for all internet traffic and might only have one upstream ISP at all. You should be able to see this by looking at the whois entry of your ISP AS (go to www.arin.net or www.ripe.net).
In fact thinking about the specific scenario you described, it might be also that your private AS in the AS path was blocked and thus not reachable.
Hard to tell afterwards.
In case you run into those problems again, I would go to traceroute.org, which has a list of looking glasses and route server, which allow you to investigate different ISP BGP tables. from there you can see your network and what AS path and other settings there are, or where it is missing.
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...
Attached policy provides CLI access to the Cisco 4G router over text messaging. Two files are in the attached .tar file:
2. PDF with instructions on how to load and use the .tcl file.