Hi,
Does anyone have the solution to this lab? I tried with next-hop-self command but no results.
BGP Next hop self
Scenario:
As a junior networking engineer you were always fascinated with science fiction movies, that's why you are now working at a company specialized in special effects. The closest you got to light speed was sending bits and bytes with electricity through wires...nevertheless there is a task waiting for you. You need to configure BGP between your network (AS100) and the service provider (AS100). Setting up BGP was no problem for you, but users behind router Luke are complaining they can't access networks in AS 200. Time for you to solve this problem...you feel the force is strong within you so this should be a piece of cake!
Goal:
- All IP addresses have been preconfigured as specified in the topology picture.
- Configure IBGP between router Hansolo and Luke, use AS 100, use the loopback0 interfaces as source for BGP.
- Configure EBGP between router Hansolo and Leia.
- Ensure both BGP neighbor relationships are up.
- Router HanSolo: Advertise the 192.168.12.0/24 network into BGP.
- Router Leia: Advertise the 3.3.3.0 /24 on the loopback interface into BGP.
- Ensure you can ping this network from router Hansolo.
- Try to ping this network from router Luke, why does this fail?
- Fix this problem by using a BGP command on router Hansolo. You are not allowed to advertise the 192.168.13.X network in BGP.
IOS:
c3640-jk9s-mz.124-16.bin
Topology:
Video Solution:
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Comments (14)
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ReneMolenaar 2011-01-19 21:39:34Try a show ip bgp on router Luke. It'll show you the next-hop address for the network router Leia is advertising.
Now take a look and see if this next-hop address if reachable....it probably isn't.
There are 2 ways to fix this:
1) Make the next-hop reachable by using a static or routing protocol.
2) Use next-hop-self on router HanSolo so the next-hop address for router Luke changes.Good luck!
Rene
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lcguy 2011-01-20 15:35:23router bgp 100
no synchronization
bgp log-neighbor-changes
neighbor 192.168.12.3 remote-as 200
neighbor 192.168.23.2 remote-as 100
neighbor 192.168.23.2 next-hop-self
no auto-summary--------
Still can't figure out how to reach 1.1.1.1.
Even trying with static router also failed
next hop address in Router Luke show correctly as belowBGP table version is 8, local router ID is 192.168.23.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incompleteNetwork Next Hop Metric LocPrf Weight Path
*>i1.1.1.0/24 192.168.23.1 0 100 0 200 i
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lcguy 2011-01-26 14:02:00
Hi Rene,
I got it. It's really good lab.Thanks again.
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ReneMolenaar 2011-01-31 05:00:41
Keep in mind that you need to check all the BGP routers 'Routing Tables'. Perhaps you only have 'one way' reachability and the ip packets don't know their way back...
Check every routing table and see if you have full reachability.
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Allex 2011-04-02 19:09:07Thank you.
Good practice.
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Sharky 2011-04-20 10:54:08Hey I fired up tha lab and it is working like I thought. I entered the next hop self command on hansolo. So if I ping the network 1.1.1.1 from Luke it failed because there it no way back on Leia. Leia does not know how to reach Luke.
My solution fire up a default route or : ip route 192.168.23.0 255.255.255.0 s0/0 . I am right?
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ReneMolenaar 2011-04-21 16:54:52
@Sebastian,
Uh-oh shame on you for using default / static routes in a BGP lab! ;D
I changed the lab task to make sure to advertise 192.168.23.0 into BGP, otherwise router Leia will indeed not know the way back to router Luke.
Rene
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veka 2012-03-26 04:07:29Hi Rene,
I have one question about this Lab...
When you trying to ping Lo 3.3.3.3 from Luke it works. I was wondering what do you suggest in the other way: when you try to ping Lo 2.2.2.2 from Leia? I tried with advertising first that network 2.2.2.0 from Luke and then with advertising the network 192.168.13.0 from HanSolo. And the ping from Leia to Lo 2.2.2.2 then works.
I just wanna know if that's ok and the appropriate way for this situation? I mean does it make sense if I do something like that? Thanks in advance!
Veka;D;D;D;D;D
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ReneMolenaar 2012-04-02 09:20:26
Hi Veka,
You already know the answer but just for anyone else that is wondering...
When a router learns something through EBGP and advertises it through IBGP to routers in the same AS it will not change the next-hop IP address. This can sometimes cause issues with reachability if the next-hop IP address is not reachable.
Best way to solve and check what is going on is to use the "show ip bgp" command to see the advertised network(s) and the next-hop IP address. Next step is to make sure the next-hop IP address is reachable. If it's not we need to advertise additional networks and/or use the "next-hop-self" command to change the next-hop IP address.
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veka 2012-03-26 04:09:13
OMG how many smileys!
I have not even noticed.Sorry about that :/
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ReneMolenaar 2012-04-02 09:21:35
I rather see smileys than angry faces
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easter0009 2012-05-02 02:24:45Hi Rene
I was working on this lab, every thing was perfect. however i dont understand why did you say "Router HanSolo: Advertise the 192.168.12.0/24 network into BGP."
I also checked and found that without network 192.168.12.0/24 " its impossible to reach to 3.3.3.3 from Router Luke.If our final task to put everything into BGP then why do we use Internal routing protocol to support BGP. when we know that rules like Split horizon and synchronization also working in BGP.
we can also do redistribution to achieve this task or do only BGP on all router.
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ReneMolenaar 2012-05-02 09:49:56
Hi,
Quote:I was working on this lab, every thing was perfect. however i dont understand why did you say "Router HanSolo: Advertise the 192.168.12.0/24 network into BGP."
I also checked and found that without network 192.168.12.0/24 " its impossible to reach to 3.3.3.3 from Router Luke.You need to do this because router Leia will receive IP packets with a source address of the 192.168.12.0/24 subnet. If you don't advertise this network Leia has no idea where to return the IP packets to.
Quote:If our final task to put everything into BGP then why do we use Internal routing protocol to support BGP. when we know that rules like Split horizon and synchronization also working in BGP.
we can also do redistribution to achieve this task or do only BGP on all router.An IGP is commonly used for BGP because for IBGP because of two reasons:
- IBGP has to be full mesh so you have to configure BGP neighbors with all routers, not just the neighbors that are directly connected. Without a routing protocol your router only knows about it's "directly connected" networks so we need to use an IGP like OSPF so it can learn about other networks so we can configure IBGP peerings between all routers.
- For IBGP it's best practice to configure the BGP peering between loopback interfaces. Physical interfaces can go do down and this will kill our BGP peering. If we use loopbacks we have an IGP to calculate another route to the loopback interface.
Does that make sense?
Best Regards,
Rene