03-02-2010 01:57 PM - edited 03-04-2019 07:40 AM
Hi, this is a very simple configuration. My intention is to set MED on R1 and later make that as my preferred traffic traffic entry point.
I see on R1 'show ip bgp' that incoming traffic is correctly identified as AS '200'.
However MED is not being set on R1 as '999'.
Can you please help me find out why not?
R1(AS 100)-------------------R2(AS 200)
On R1 I do
R1#show ip bgp
BGP table version is 5, local router ID is 10.2.80.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 2.2.2.2/32 10.2.47.193 0 0 200 i
*> 10.2.0.0/16 0.0.0.0 32768 i
*> 10.2.44.0/24 0.0.0.0 0 32768 i
*> 10.2.90.0/24 10.2.47.193 0 0 200 i
R1#
!
interface Loopback0
no ip address
!
interface Loopback1
ip address 10.2.80.1 255.255.255.0
!
interface Loopback4
ip address 10.2.44.1 255.255.255.0
!
interface FastEthernet0/0
ip address 10.2.47.204 255.255.255.240
speed 100
full-duplex
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
router bgp 100
no synchronization
bgp log-neighbor-changes
network 10.2.44.0 mask 255.255.255.0
aggregate-address 10.2.0.0 255.255.0.0
neighbor 10.2.47.193 remote-as 200
neighbor 10.2.47.193 route-map TO_R1 out
no auto-summary
!
ip forward-protocol nd
!
ip as-path access-list 1 permit _200$
!
ip http server
no ip http secure-server
!
!
route-map TO_R1 permit 10
match as-path 1
set metric 999
!
route-map TO_R1 permit 100
!
!
(end)
---------------------------------
R2# show ip bgp
BGP table version is 5, local router ID is 10.2.55.133
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 2.2.2.2/32 0.0.0.0 0 32768 i
*> 10.2.0.0/16 10.2.47.204 0 0 100 i
*> 10.2.44.0/24 10.2.47.204 0 0 100 i
*> 10.2.90.0/24 0.0.0.0 0 32768 i
R2#
!
desc R2 bgp statement
router bgp 200
no synchronization
bgp log-neighbor-changes
network 2.2.2.2 mask 255.255.255.255
network 10.2.90.0 mask 255.255.255.0
neighbor 10.2.47.204 remote-as 100
no auto-summary
!
Solved! Go to Solution.
03-02-2010 03:11 PM
Marlon
As always, glad to have helped. You are going to be a BGP guru by the time you have finished your labs
Jon
03-02-2010 02:13 PM
Marlon
I may not be understanding your topology but MED is set on routes going out from R1 not routes coming in to R1. MED is used to influence how traffic is sent to your AS.
So if you want to make R1 then entry point from R2 you set MED on the routes being advertised to R2.
And if you want to set MED on routes being received by R1 you need to set the MED on R2. Your config doesn't look like it is doing this.
Can you clarify ?
Jon
03-02-2010 02:24 PM
Jon, imagine I own and I have control over R1 (AS 100) router only.
So R2 (AS 200) is an ISP which is not going to change their configuration.
So if in the future I have R1 and R3 both in AS 100 connected to R2 AS 200, I am trying to make R1 as the preferred path for ingress traffic coming from the R2 AS 200 "ISP".
I really thought I could control this from the R1 side via MED. Am I wrong?
03-02-2010 02:29 PM
news2010a wrote:
Jon, imagine I own and I have control over R1 (AS 100) router only.
So R2 (AS 200) is an ISP which is not going to change their configuration.
So if in the future I have R1 and R3 both in AS 100 connected to R2 AS 200, I am trying to make R1 as the preferred path for ingress traffic coming from the R2 AS 200 "ISP".
I really thought I could control this from the R1 side via MED. Am I wrong?
Marlon
You can do this with MED and your understanding is correct. But your matching criteria in the route-map is -
ip as-path access-list 1 permit _200$
what is that meant to match because the routes when they are sent to R2 will not have AS 200 in them. MED is added to your routes as they are sent out not to R2's routes as they are received.
Jon
03-02-2010 02:54 PM
That is true. If it is leaving the AS so AS=200 is not there.
Then I am trying now using a prefix-list. It should work.
However I do 'clear ip bgp*' on R1 and I still do not see the metric set. Any hint?
R1#sho ip prefix-list
ip prefix-list LIST_ENG: 1 entries
seq 5 permit 10.2.0.0/16 le 32
R1#show run | s bgp
router bgp 100
no synchronization
bgp log-neighbor-changes
network 10.2.20.0 mask 255.255.255.0
aggregate-address 10.2.0.0 255.255.0.0
neighbor 10.2.47.193 remote-as 200
neighbor 10.2.47.193 route-map SETMED out
no auto-summary
R1#show route-map
route-map SETMED, permit, sequence 10
Match clauses:
ip address (access-lists): LIST_ENG
Set clauses:
metric 999
Policy routing matches: 0 packets, 0 bytes
route-map SETMED, permit, sequence 100
Match clauses:
Set clauses:
Policy routing matches: 0 packets, 0 bytes
1#
R1#show ip bgp
BGP table version is 6, local router ID is 10.2.30.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 10.2.0.0/16 0.0.0.0 32768 i
*> 10.2.20.0/24 0.0.0.0 0 32768 i
*> 192.168.1.0 10.2.47.193 0 0 200 i
R1#
03-02-2010 03:02 PM
Ding. I see it on R2 actually. So there is where the MED is set... sure it makes sense.
Thanks for your help.
03-02-2010 03:11 PM
Marlon
As always, glad to have helped. You are going to be a BGP guru by the time you have finished your labs
Jon
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