[nsp] BGP filter issue
Nikos Leontsinis
nikos at oteglobe.net
Fri Jan 30 11:15:19 EST 2004
Here is a filter list you can use
ip as-path access-list 6 permit _(19262|x|y)$
Where x & y are your customer's customers in other words the Ass you
want to receive
and subsequently propagate. Your problem was that you were blocking the
prefixes in question
/nikos
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Alban Dani
> Sent: 30 January 2004 16:19
> To: 'Sean Mathias'
> Cc: cisco-nsp at puck.nether.net
> Subject: RE: [nsp] BGP filter issue
>
>
> Hi Sean,
>
> Here is some of the output from the command you suggested.
> This output is taken from another router that has the same
> filter applied. For the moment I can not put the filter back
> on the original router.
>
> router#sh ip bgp regexp ^19262 [0-9]+$
> BGP table version is 79535136, local router ID is
> xxx.xxx.xxx.xxx Status codes: s suppressed, d damped, h
> history, * valid, > best, i - internal Origin codes: i - IGP,
> e - EGP, ? - incomplete
>
> Network Next Hop Metric LocPrf Weight Path
> *> 128.6.0.0 130.156.250.93 0 0
> 19262 46 i
> *> 128.235.0.0 130.156.250.93 0 0
> 19262 4246
> i
> *> 128.235.160.0/20 130.156.250.93 0 0
> 19262 4246
> i
> *> 128.235.240.0/23 130.156.250.93 0 0
> 19262 4246
> i
> *> 130.68.0.0/17 130.156.250.93 0 0
> 19262 205 i
> *> 130.68.128.0/18 130.156.250.93 0 0
> 19262 205 i
> *> 130.68.192.0/19 130.156.250.93 0 0
> 19262 205 i
> *> 130.156.17.0/24 130.156.250.93 0 0
> 19262 18794
> i
> *> 130.156.142.0/23 130.156.250.93 2654 0
> 19262 26635
> i
> *> 130.156.144.0/22 130.156.250.93 2654 0
> 19262 26635
> i
> *> 130.156.148.0/24 130.156.250.93 2654 0
> 19262 26635
> i
> *> 130.219.0.0/19 130.156.250.93 0 0
> 19262 11094
> ?
> *> 130.219.0.0 130.156.250.93 0 0
> 19262 11094
> i
> *> 130.219.32.0/21 130.156.250.93 0 0
> 19262 11094
> ?
> *> 130.219.40.0/21 130.156.250.93 0 0
> 19262 11094
> ?
> *> 130.219.48.0/20 130.156.250.93 0 0
> 19262 11094
> ?
> *> 130.219.64.0/19 130.156.250.93 0 0
> 19262 11094
> ?
> *> 130.219.96.0/20 130.156.250.93 0 0
> 19262 11094
> ?
>
> Thanks for your help,
>
> Alban
>
> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Sean Mathias
> Sent: Thursday, January 29, 2004 5:48 PM
> To: Alban Dani; cisco-nsp at puck.nether.net
> Subject: RE: [nsp] BGP filter issue
>
> With the filter in place, can you look at the output of show
> ip bgp regexp ^19262 [0-9]+$ to see if it is matching as you
> expected it to?
>
> Sean Mathias
> CCIE #12779
> 206-920-0301
> seanm at prosolve.com
>
>
> -----Original Message-----
> From: Alban Dani [mailto:adani at stevens.edu]
> Sent: Thursday, January 29, 2004 1:14 PM
> To: cisco-nsp at puck.nether.net
> Subject: [nsp] BGP filter issue
>
>
> Hello,
>
>
>
> Recently I experienced a weird issue with our internet connection.
>
>
>
> We have a Cisco 7200 connected to our ISP ( Verizon).
>
> A month ago we applied a bgp filter on the inbound that would
> accept bgp routing updates only from our neighbor AS and the
> one next to it.
>
>
>
> ip as-path access-list 6 permit ^19262$
>
> ip as-path access-list 6 permit ^19262 [0-9]+$
>
> ip as-path access-list 6 deny .*
>
>
>
> Last week we started having issues with the internet
> connection for several employees that connected remotely to
> our network. After some research we figured that people that
> were connected to ISP-s that were no more then two AS hops
> from us were having the problem ( and we could find their
> networks in the bgp table ). On the other hand people who
> were more then two AS hops away were just fine. Their
> networks could not be found in the bgp table (as excpected
> because of the filter ) and they were taking the default
> route outside.
>
>
>
> We took the filter out today and everything is back to normal.
>
>
>
> Can anybody explain this? Is it a bug? A design flow? Is it the ISP?
>
>
>
>
>
> Thanks in advance
>
>
>
> Alban
>
>
>
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