[c-nsp] MED on vpnv4 routes
Zaheer Aziz
zaziz at cisco.com
Thu Aug 12 11:29:41 EDT 2004
At 10:16 AM 8/12/2004 -0500, Timothy.Hall at alltel.com wrote:
>I set the med on the ibgp neighbors inbound. I don't alter the routes
>outbound ebgp so the med should still be advertised.
Hi Tim,
quoting directly from the source. Please read the last line
RFC 1771 BGP-4 March 1995
5.1.4 MULTI_EXIT_DISC
The MULTI_EXIT_DISC attribute may be used on external (inter-AS)
links to discriminate among multiple exit or entry points to the same
neighboring AS. The value of the MULTI_EXIT_DISC attribute is a four
octet unsigned number which is called a metric. All other factors
being equal, the exit or entry point with lower metric should be
preferred. If received over external links, the MULTI_EXIT_DISC
attribute may be propagated over internal links to other BGP speakers
within the same AS. The MULTI_EXIT_DISC attribute is never
propagated to other BGP speakers in neighboring AS's.
Zaheer
>-----Original Message-----
>From: Zaheer Aziz [mailto:zaziz at cisco.com]
>Sent: Thursday, August 12, 2004 10:06 AM
>To: Hall, Timothy
>Cc: zaziz at cisco.com; cisco-nsp at puck.nether.net
>Subject: RE: [c-nsp] MED on vpnv4 routes
>
>
>At 09:52 AM 8/12/2004 -0500, Timothy.Hall at alltel.com wrote:
> >I am setting the med in the gsr:
>
>
>I does not look like that you are setting the MED for neighbor 10.0.200.2
>
>Here is your relevant config.
>
>neighbor 10.0.200.2 activate
>neighbor 10.0.200.2 route-map ebgp-out out
>
>route-map ebgp-out permit 10
> match as-path 100
>!
>route-map ebgp-out deny 20
>
>
>ip as-path access-list 100 permit ^$
>ip as-path access-list 100 deny all
>
>where is the MED setting for this neighbor in AS 65000 ?
>By default MED is cleared when an update crosses the AS
>Hope this helps
>Zaheer
>
>
>
> >router bgp 65001
> > no bgp default ipv4-unicast
> > bgp log-neighbor-changes
> > bgp deterministic-med
> > bgp graceful-restart restart-time 120
> > bgp graceful-restart stalepath-time 360
> > bgp graceful-restart
> > neighbor 10.0.200.2 remote-as 65000
> > neighbor 192.168.0.6 remote-as 65001
> > neighbor 192.168.0.6 update-source Loopback0
> > neighbor 192.168.0.7 remote-as 65001
> > neighbor 192.168.0.7 update-source Loopback0
> > neighbor 192.168.0.22 remote-as 65001
> > neighbor 192.168.0.22 update-source Loopback0
> > !
> > address-family ipv4
> > auto-summary
> > no synchronization
> > exit-address-family
> > !
> > address-family vpnv4
> > neighbor 10.0.200.2 activate
> > neighbor 10.0.200.2 send-community both
> > neighbor 10.0.200.2 route-map ebgp-in in
> > neighbor 10.0.200.2 route-map ebgp-out out
> > neighbor 192.168.0.6 activate
> > neighbor 192.168.0.6 next-hop-self
> > neighbor 192.168.0.6 send-community both
> > neighbor 192.168.0.6 route-map set-med-high in
> > neighbor 192.168.0.6 route-map set-loc-pref out
> > neighbor 192.168.0.7 activate
> > neighbor 192.168.0.7 next-hop-self
> > neighbor 192.168.0.7 send-community both
> > neighbor 192.168.0.22 activate
> > neighbor 192.168.0.22 next-hop-self
> > neighbor 192.168.0.22 send-community both
> > neighbor 192.168.0.22 route-map set-med-low in
> > neighbor 192.168.0.22 route-map set-loc-pref out
> > exit-address-family
> > !
> > address-family ipv4 vrf test-vrf
> > no auto-summary
> > no synchronization
> > exit-address-family
> >!
> >ip classless
> >!
> >ip extcommunity-list 1 permit rt 65000:1
> >ip bgp-community new-format
> >ip community-list 4 permit 65000:4
> >ip community-list 14 permit 65000:14
> >ip as-path access-list 100 permit ^$
> >ip as-path access-list 100 deny all
> >!
> >!
> >ip prefix-list ROUTE_SOURCE seq 5 permit 192.168.0.22/32
> >access-list 10 permit 192.168.0.22
> >access-list 10 deny any
> >access-list 20 permit 192.168.0.6
> >access-list 20 deny any
> >route-map set-med-high permit 10
> > set metric 100
> >!
> >route-map set-loc-pref permit 10
> > match community 4
> > set local-preference 200
> >!
> >route-map set-loc-pref permit 20
> > match community 14
> >!
> >route-map ebgp-in permit 10
> > match extcommunity 1
> > set extcomm-list 1 delete
> > set extcommunity rt 65001:1
> >!
> >route-map ebgp-out permit 10
> > match as-path 100
> >!
> >route-map ebgp-out deny 20
> >!
> >route-map set-med-low permit 10
> > set metric 50
> >
> >----------------------------------------------
> >
> >tim
> >
> >
> >
> >At 08:30 AM 8/12/2004 -0500, Timothy.Hall at alltel.com wrote:
> > >Here is the debug output for the GSR (sender):
> >
> >One more question
> >
> >Are you setting the MEDs on the ASBR(GSR) or is it set somewhere else in
> >65000.
> >relevant configs from GSR and 7200 would be helpful as well.
> >Thans
> >Zaheer
> >
> >
> > >*Aug 12 11:41:09.418: %BGP-5-ADJCHANGE: neighbor 10.0.200.2 Up
> > >r19#
> > >*Aug 12 11:41:09.418: BGP(2): 10.0.200.2 send UPDATE (format)
> > >192.168.0.22:1:10.0.133.0/30, next 10.0.200.1, metric 50, path , extended
> > >community RT:65001:1
> > >*Aug 12 11:41:09.418: BGP(2): 10.0.200.2 send UPDATE (format)
> > >192.168.0.6:1:10.0.136.0/30, next 10.0.200.1, metric 100, path , extended
> > >community RT:65001:1
> > >
> > >Here is the debug output for the 7200 (receiver):
> > >
> > >w0d: BGP: Import walker start version 1, end version 3
> > >1w0d: BGP: ... start import cfg version = 2
> > >1w0d: BGP: Prefix 192.168.0.6:1:10.0.136.0/30 to be imported as
> > >0:0:10.0.136.0/30 -- Permitted
> > >nexthop 10.0.200.1, origin i, path 65001, extended community RT:65001:1
> > >1w0d: Path added
> > >1w0d: BGP: Prefix 192.168.0.22:1:10.0.133.0/30 to be imported as
> > >0:0:10.0.133.0/30 -- Permitted
> > >nexthop 10.0.200.1, origin ?, path 65001, extended community RT:65001:1
> > >1w0d: Path added
> > >1w0d: BGP(2): Revise route installing 1 of 1 route for 10.0.133.0/30 ->
> > >10.0.200.1 to test IP table
> > >1w0d: BGP(2): Revise route installing 1 of 1 route for 10.0.136.0/30 ->
> > >10.0.200.1 to test IP table
> > >
> > >Last, here is the sh ip bgp vpnv4 * output:
> > >
> > >Network Next Hop Metric LocPrf Weight Path
> > >Route Distinguisher: 0:0
> > >*> 10.0.133.0/30 10.0.200.1 0 65001 ?
> > >*> 10.0.136.0/30 10.0.200.1 0 65001 i
> > >
> > >As you can see, metric appears to be sent, but not received???
> > >
> > >tim
> > >
> > >
> > >
> > >At 04:20 PM 8/11/2004 -0500, Timothy.Hall at alltel.com wrote:
> > > >We are having a problem with some lab testing. We set up two AS's doing
> > > >interprovider VPN, each AS has two ASBR's. The ASBR's are set up
> with ebgp
> > > >advertising only the vpnv4 routes. We set the MED for the routes so that
> > > >we would know which inter-AS link traffic would take. One border
> router is
> > > >an M-series, the other is a GSR. Problem is the GSR is not sending
> the vpn
> > > >routes with the MED set. The debug ip bgp update output shows that
> the MED
> > > >is set and the router thinks it is advertising properly, however the
> other
> > > >side does not indicate that it is receiving the MED attribute. Also, it
> > > >doesn'ty matter whether the receiving router is an M-series or a Cisco
> > > >router. Problem occurs in both cases.
> > >
> > >Please provide the debugs from sender and receiver for any one of the
> > >prefixes in question.
> > >
> > >Zaheer
> > >
> > >
> > > >GSR is running 12.0(27)S2.
> > > >
> > > >Anyone have any ideas?
> > > >
> > > >Thanks,
> > > >Tim
> > > >
> > > >*********************************************************************
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>The information contained in this message, including attachments, may contain
>privileged or confidential information that is intended to be delivered
>only to the
>person identified above. If you are not the intended recipient, or the person
>responsible for delivering this message to the intended recipient, ALLTEL
>requests
>that you immediately notify the sender and asks that you do not read the
>message or its
>attachments, and that you delete them without copying or sending them to
>anyone else.
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