BGP IBGP/EBGP Local Preference MED

I don't see a download link on this one???

Just fixed it thanks for the letting me know!

I like to check my answer against the correct answer. Are the answers posted here?

It is not possible to only achieve this goal only via Berry. With MED, smaller is better. So configuring a MED on Berry (>0) will only have as result that the ISP will still prefer his route over Cherry. (Since on Cherry the MED is still 0). You need Cherry to acomplish this goal.

ummm where is the solution????

I don't have the solutions for this lab right now, i'll be adding them later...takes time.

Thanks for taking the time to create these labs. They are excellent and not having the answers available just means we have to try a bit harder!

Cheers
Michael

i just tried this lab today, and managed to finish it. like the previous poster said, it is not possible to only modify Berry to take the Berry-ISP path for all traffic toward AS100, because the default metric is already 0. I tried to decrease the metric to -1, but it is not possible.

this is my partial config for Berry.
router eigrp 10
network 2.0.0.0
network 192.168.12.0
no auto-summary
!
router bgp 100
no synchronization
bgp log-neighbor-changes
network 2.2.2.0 mask 255.255.255.0
network 192.168.12.0
neighbor 1.1.1.1 remote-as 100
neighbor 1.1.1.1 update-source Loopback0
neighbor 192.168.23.3 remote-as 200
neighbor 192.168.23.3 route-map policy1 in
neighbor 192.168.23.3 route-map policy2 out
no auto-summary
!
route-map policy1 permit 10
set local-preference 300
!
route-map policy2 permit 10
set metric -1

config for Cherry is very similar but for local preference I made it lower (say 150) so that traffic going outbound to AS200 will prefer Berry-ISP path because Berry's local preference (in AS100) is 300 (can be any value, it's up to you).

you are right about this. I'm going to change the lab a bit But i guess you get the idea...play with the MED will influence the path that it'll take

Thanks for the comment!

in my opinion these two routes (from ISP perspective) are pretty equal.

the comparison process goes below step #8 (N WLLA OMNI) and actually ISP router selects the route which exist longer than another - it means who comes up first wins the competition (for the first time).

you can reset "the best" route and the another one becomes "the best" because now it exists longer.

so ISP could select route over Berry as well.

Quote:

R3#sh ip bgp 192.168.12.0/24 lo
BGP table version is 14, local router ID is 3.3.3.3
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
* 192.168.12.0 192.168.13.1 0 0 100 i
*> 192.168.23.2 0 0 100 i
R3#
R3#
R3#clear ip bgp 192.168.23.2
R3#
*Mar 1 00:21:59.903: G;P-5-ADJCHANGE: neighbor 192.168.23.2 Down User reset
R3#
*Mar 1 00:221.191: G;P-5-ADJCHANGE: neighbor 192.168.23.2 Up
R3#
R3#
R3#sh ip bgp 192.168.12.0/24 lo
BGP table version is 19, local router ID is 3.3.3.3
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
* 192.168.12.0 192.168.23.2 0 0 100 i
*> 192.168.13.1 0 0 100 i
R3#

This lab has some errors, i'll have to fix it

lab is awesome, the only error was instead of changing the MED on Berry, change it on Cherry to some high value and leave the MED on Berry alone. By default its 0, and changing the MED on Cherry to any value above 0 will cause the ISP to take the route via Berry now as its the lower MED (0).

Thanks for the lab.

Dear a||

Can any one share the full lab config.

thanx
KD

Hi, I'm not able to open the .net file with GNS3 v0.7.3 it says:
"*** Error: errors during loading of the topology file, please correct them."

task #2 "Do not advertise the links between AS100 and AS200 in EIGRP"

This line gives me the impression that i should also configure eigrp on the ISP with AS200.. is that true? It's not clear where AS200 is or what i'm supposed to do with it at this point.

Hi Terelle,

I should have added AS 100 and AS 200 in the picture...The yellow circle is AS 100, the ISP is AS 200.

When you are connecting to an ISP you are not going to run an IGP with them (think on an Internet scale). That's what BGP is for.

You shouldn't advertise the links in between AS 100 and AS 200 in EIGRP nor send EIGRP updates on them. Configure BGP between the different ASes and exchange routing information with BGP.

Rene

hi

I have a question about reachablity of the 4.4.4.4 network from kerry. Why we couldn t reach the network before we advertised the connections in the
AS 100 via BGP. We have got the necessary routes in the routing table learned via EIGRP before advertised them.
If it is not enough via learning EIGRP we have just enable it to learn loopbacks?

I really confused about that.

Hi w2ccip,

I'm not entirely sure what you mean

Within AS 100 we use loopbacks for the IBGP peering. We do this because otherwise a link failure could result in a BGP neighbor going down because the IP address of the physical interface is no longer reachable. We use EIGRP to advertise the loopbacks so we can use those for the BGP peering.

Network 4.4.4.0/24 is advertised through EBGP from the ISP router to AS 100 and since we run IBGP on every router in AS 100 we have reachability.

i want to say that why we have advertised the 192.168.12.0 and 192.168.13.0 networks. they have already in the routing table via EIGRP. Isnt it enough to advertised with EIGRP?

I got the problem at last.
thanks for your considerations.

Hi Muhammed,

Glad to hear you got it. In short this is what we do:

- Use an IGP to advertise the loopback interfaces within the AS.
- Configure IBGP using the loopback interfaces.
- Configure EBGP between the autonomous systems.

Good luck with your studying!

Rene

thanks for these labs. they are extremely helpful to reinforce the concepts.

thanks for your comment!

Hi Rene,
Can you please enable the option to download the labs in the pdf format.

I think I will, downside is that it will add additional code to the site which makes it slower.

For the moment I would recommend to use a PDF printer like "cute pdf writer".

Hi,

I have done the following configurations in four routers tried to do the things in simple way as I am trying to grab these valuable things.

Please find the configurations of the routers one by one:-

Kerry Router :-

interface Loopback0
ip address 1.1.1.1 255.255.255.0
!
interface FastEthernet0/0
description connected to BERRY
ip address 192.168.13.1 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
description connected to CHERRY
ip address 192.168.12.1 255.255.255.0
duplex auto
speed auto
!
interface Serial1/0
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/1
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/3
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/4
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/5
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/6
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/7
no ip address
shutdown
serial restart-delay 0
!
router eigrp 100
network 1.0.0.0
network 192.168.12.0
network 192.168.13.0
distance 220 0.0.0.0 255.255.255.255
no auto-summary
!
router bgp 100
no synchronization
bgp log-neighbor-changes
network 1.1.1.0 mask 255.255.255.0
neighbor 2.2.2.2 remote-as 100
neighbor 2.2.2.2 update-source Loopback0
neighbor 3.3.3.3 remote-as 100
neighbor 3.3.3.3 update-source Loopback0
no auto-summary
!
=============================================
I changed the AD of EIGRP to 220 as I wanted to show the BGP related paths as AD of IBGP is 200 & that's why it was showing rib-failure previously. I changed these AD settings with all other routers i.e. Cherry & Berry
============================================
Cherry

interface Loopback0
ip address 2.2.2.2 255.255.255.0
!
interface FastEthernet0/0
description connected to BERRY
ip address 192.168.23.2 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
description connected to KERRY
ip address 192.168.12.2 255.255.255.0
duplex auto
speed auto
!
interface Serial1/0
description connected to ISP
ip address 192.168.24.2 255.255.255.0
serial restart-delay 0
!
interface Serial1/1
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/3
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/4
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/5
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/6
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/7
no ip address
shutdown
serial restart-delay 0
!
router eigrp 100
network 2.0.0.0
network 192.168.12.0
network 192.168.23.0
distance 220 0.0.0.0 255.255.255.255
no auto-summary
!
router bgp 100
no synchronization
bgp log-neighbor-changes
network 2.2.2.0 mask 255.255.255.0
network 192.168.12.0
network 192.168.23.0
neighbor 1.1.1.1 remote-as 100
neighbor 1.1.1.1 update-source Loopback0
neighbor 1.1.1.1 next-hop-self
neighbor 3.3.3.3 remote-as 100
neighbor 3.3.3.3 update-source Loopback0
neighbor 4.4.4.4 remote-as 200
neighbor 4.4.4.4 ebgp-multihop 2
neighbor 4.4.4.4 update-source Loopback0
neighbor 4.4.4.4 route-map MED out
no auto-summary
!
ip classless
ip route 4.4.4.4 255.255.255.255 192.168.24.4
no ip http server
no ip http secure-server
!
!
!
route-map MED permit 1
set metric 150

===============================================
Berry

interface Loopback0
ip address 3.3.3.3 255.255.255.0
!
interface FastEthernet0/0
description connected to CHERRY
ip address 192.168.23.3 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
description connected to KERRY
ip address 192.168.13.3 255.255.255.0
duplex auto
speed auto
!
interface Serial1/0
description connected to ISP
ip address 192.168.34.3 255.255.255.0
serial restart-delay 0
!
interface Serial1/1
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/3
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/4
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/5
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/6
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/7
no ip address
shutdown
serial restart-delay 0
!
router eigrp 100
network 3.0.0.0
network 192.168.13.0
network 192.168.23.0
distance 220 0.0.0.0 255.255.255.255
no auto-summary
!
router bgp 100
no synchronization
bgp log-neighbor-changes
network 3.3.3.0 mask 255.255.255.0
network 192.168.13.0
network 192.168.23.0
neighbor 1.1.1.1 remote-as 100
neighbor 1.1.1.1 update-source Loopback0
neighbor 1.1.1.1 next-hop-self
neighbor 2.2.2.2 remote-as 100
neighbor 2.2.2.2 update-source Loopback0
neighbor 4.4.4.4 remote-as 200
neighbor 4.4.4.4 ebgp-multihop 2
neighbor 4.4.4.4 update-source Loopback0
neighbor 4.4.4.4 route-map MED out
no auto-summary
!
ip classless
ip route 4.4.4.4 255.255.255.255 192.168.34.4
no ip http server
no ip http secure-server
!
!
!
route-map MED permit 1
set metric 50
==============================================

ISP

interface Loopback0
ip address 4.4.4.4 255.255.255.0
!
interface FastEthernet0/0
no ip address
shutdown
duplex auto
speed auto
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
interface Serial1/0
description connected to CHERRY
ip address 192.168.24.4 255.255.255.0
serial restart-delay 0
!
interface Serial1/1
description connected to BERRY
ip address 192.168.34.4 255.255.255.0
serial restart-delay 0
!
interface Serial1/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/3
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/4
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/5
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/6
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/7
no ip address
shutdown
serial restart-delay 0
!
router bgp 200
no synchronization
bgp log-neighbor-changes
network 4.4.4.0 mask 255.255.255.0
neighbor 2.2.2.2 remote-as 100
neighbor 2.2.2.2 ebgp-multihop 2
neighbor 2.2.2.2 update-source Loopback0
neighbor 3.3.3.3 remote-as 100
neighbor 3.3.3.3 ebgp-multihop 2
neighbor 3.3.3.3 update-source Loopback0
no auto-summary
!
ip classless
ip route 2.2.2.2 255.255.255.255 192.168.24.2
ip route 3.3.3.3 255.255.255.255 192.168.34.3

==============================================

Here I just wanted to explore the MED & wanted that all the traffic should reach AS 200 via berry that's why I set the metric 50 in Berry.

Now how could I check that the traffic is moving to ISP via Berry?

May be I have done so many silly things but I need to clear the ideas about the BGP activities.

It's also showing some abnormal behaviour in Kerry Router:-

KERRY#sh ip bgp s
BGP router identifier 1.1.1.1, local AS number 100
BGP table version is 1, main routing table version 1
6 network entries using 606 bytes of memory
8 path entries using 384 bytes of memory
2 BGP path attribute entries using 180 bytes of memory
1 BGP AS-PATH entries using 24 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 1194 total bytes of memory
BGP activity 28/22 prefixes, 52/44 paths, scan interval 60 secs

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
2.2.2.2 4 100 544 538 1 0 0 000:26 4
3.3.3.3 4 100 555 547 1 0 0 000:25 4
KERRY#ping 2.2.2.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
KERRY#ping 3.3.3.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

Now again it's pinging. I donno why this is happening? strange.
Let me also tell you that I added these networks in BGP As 100 in Kerry.
i.e.

network 192.168.12.0
network 192.168.13.0

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/31/56 ms
KERRY#ping 3.3.3.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 12/40/60 ms
KERRY#