EIGRP and split-horizon

Discussion in 'Cisco' started by Tosh, Apr 2, 2006.

  1. Tosh

    Merv Guest

    Do I have to disable split horizon in order to be sure that Hub1 will never
    stop advertising his routes to the local lan?

    I do not believe so.

    perhaps

    hub1 should have two topo entries just like hub2 - there is definitely
    is a problem here
     
    Merv, Apr 5, 2006
    #21
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  2. Tosh

    Tosh Guest

    hub1 should have two topo entries just like hub2 - there is definitely
    Do yuou think that split horizon has nothing to do with it?
    Today I'll try to filter a route from hub1 to switch1 and see what happens.
    Thanks again.
    Bye,
    Tosh.
     
    Tosh, Apr 5, 2006
    #22
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  3. Tosh

    Merv Guest

    What is the EIGRP router-id on hub1?

    see via "show ip eigrp topo" command

    #sh ip eigrp topo
    IP-EIGRP Topology Table for AS(10)/ID(201.64.0.201)
     
    Merv, Apr 5, 2006
    #23
  4. Tosh

    Tosh Guest

    What is the EIGRP router-id on hub1?
    IP-EIGRP Topology Table for AS(10)/ID(11.22.33.44)

    This address (purged) is a loopback configured on the router, does it have
    something to do with our issue?
    Tnx,
    Tosh.
     
    Tosh, Apr 5, 2006
    #24
  5. Tosh

    Tosh Guest

    Hi Merv,
    I tried to filter the announcements made by Hub1 to the local lan so that
    Hub1 dosn't announce anymore the network 192.168.45.0/24 learned from the
    outside.
    These are the topology details before the filtering:

    Hub1#sh ip eigrp top 192.168.45.0/24
    IP-EIGRP (AS 100): Topology entry for 192.168.45.0/24
    State is Passive, Query origin flag is 1, 1 Successor(s), FD is 307200
    Routing Descriptor Blocks:
    172.17.3.1 (FastEthernet0/1), from 172.17.3.1, Send flag is 0x0
    Composite metric is (307200/281600), Route is External
    Vector metric:
    Minimum bandwidth is 10000 Kbit
    Total delay is 2000 microseconds
    Reliability is 255/255
    Load is 25/255
    Minimum MTU is 1500
    Hop count is 1
    External data:
    Originating router is 172.17.3.1
    AS number of route is 65535
    External protocol is BGP, external metric is 0
    Administrator tag is 1 (0x00000001)

    Switch1#sh ip eigrp top 192.168.45.0/24
    IP-EIGRP (AS 100): Topology entry for 192.168.45.0/24
    State is Passive, Query origin flag is 1, 1 Successor(s), FD is 5427200
    Routing Descriptor Blocks:
    172.16.3.1 (Vlan3), from 172.16.3.1, Send flag is 0x0
    Composite metric is (5427200/307200), Route is External
    Vector metric:
    Minimum bandwidth is 10000 Kbit
    Total delay is 202000 microseconds
    Reliability is 255/255
    Load is 25/255
    Minimum MTU is 1500
    Hop count is 2
    External data:
    Originating router is 172.17.3.1
    AS number of route is 65535
    External protocol is BGP, external metric is 0
    Administrator tag is 1 (0x00000001)
    172.16.5.4 (Vlan5), from 172.16.5.4, Send flag is 0x0
    Composite metric is (7419392/2299392), Route is External
    Vector metric:
    Minimum bandwidth is 2048 Kbit
    Total delay is 241000 microseconds
    Reliability is 255/255
    Load is 1/255
    Minimum MTU is 1500
    Hop count is 2
    External data:
    Originating router is 172.17.5.1
    AS number of route is 65522
    External protocol is BGP, external metric is 0
    Administrator tag is 1 (0x00000001

    These are the same details after the filtering:

    Switch1#sh ip eigrp top 192.168.45.0/24
    IP-EIGRP (AS 100): Topology entry for 192.168.45.0/24
    State is Passive, Query origin flag is 1, 1 Successor(s), FD is 5427200
    Routing Descriptor Blocks:
    172.16.5.4 (Vlan5), from 172.16.5.4, Send flag is 0x0
    Composite metric is (7419392/2299392), Route is External
    Vector metric:
    Minimum bandwidth is 2048 Kbit
    Total delay is 241000 microseconds
    Reliability is 255/255
    Load is 1/255
    Minimum MTU is 1500
    Hop count is 2
    External data:
    Originating router is 172.17.5.1
    AS number of route is 65522
    External protocol is BGP, external metric is 0
    Administrator tag is 1 (0x00000001)

    Hub1#sh ip eigrp top 192.168.45.0/24
    IP-EIGRP (AS 100): Topology entry for 192.168.45.0/24
    State is Passive, Query origin flag is 1, 1 Successor(s), FD is 307200
    Routing Descriptor Blocks:
    172.17.3.1 (FastEthernet0/1), from 172.17.3.1, Send flag is 0x0
    Composite metric is (307200/281600), Route is External
    Vector metric:
    Minimum bandwidth is 10000 Kbit
    Total delay is 2000 microseconds
    Reliability is 255/255
    Load is 25/255
    Minimum MTU is 1500
    Hop count is 1
    External data:
    Originating router is 172.17.3.1
    AS number of route is 65535
    External protocol is BGP, external metric is 0
    Administrator tag is 1 (0x00000001)
    172.16.3.51 (FastEthernet0/0), from 172.16.3.51, Send flag is 0x0
    Composite metric is (7421952/7419392), Route is External
    Vector metric:
    Minimum bandwidth is 2048 Kbit
    Total delay is 241100 microseconds
    Reliability is 255/255
    Load is 170/255
    Minimum MTU is 1500
    Hop count is 3
    External data:
    Originating router is 172.17.5.1
    AS number of route is 65522
    External protocol is BGP, external metric is 0
    Administrator tag is 1 (0x00000001)

    As you can see Switch1 starts to announce that paticular network as soon as
    Hub1 stops to annonce the same network.
    All other routes doesn't change state on both devices and as soon as I
    negate the filter all comes back to the original state.
    It's looking like split horizon to me.
    Bye,
    Tosh.
     
    Tosh, Apr 5, 2006
    #25
  6. Tosh

    Merv Guest

    Are you running multiple EIGRP processes on hub1 ?
     
    Merv, Apr 5, 2006
    #26
  7. Tosh

    Tosh Guest

    Are you running multiple EIGRP processes on hub1 ?Absolutely not, if you like I can send you some purged config and some
    outputs via private mail, but I don't want to abuse you.
    Tnx,
    Tosh.
     
    Tosh, Apr 5, 2006
    #27
  8. Tosh

    Merv Guest

    Configs would probably be helpful at this point.

    Also via private email the IP address of the links between
    hub1-switch1, switch1-switch2 and switch2 -hub2 as this is the only way
    to make sense of the next hop info.

    The reason I asked about the multile EIGRP proceess is that the show ip
    eigrp topo you posted yesterday show AS as 10 and todays posting
    showed the AS as 100
     
    Merv, Apr 5, 2006
    #28
  9. Tosh

    Dana Guest

    Your problem is interesting.
    If I understand what has been going on, it appears across the radio link you
    are not working properly, which is why you are asking about the split
    horizon.
    You also mentioned you are using wireless bridges. Can you ping across the
    bridge, and does the bridge perform a proper link test. I have seen where
    you can ping across the bridge, but the link test fails.
    If you already have done the above, is it possible for you to find a time
    where you can disable split horizon on both sides of the bridge without
    causing any degradation to the network, IE after business hours.
     
    Dana, Apr 5, 2006
    #29
  10. Tosh

    Tosh Guest

    The reason I asked about the multile EIGRP proceess is that the show ip
    That was the beacuse of the purge :))
     
    Tosh, Apr 6, 2006
    #30
  11. Tosh

    Tosh Guest

    If I understand what has been going on, it appears across the radio link
    The radio link is working good, there are also some servers that syncrohize
    themselves correctly across the radio link.
    I think I've got any problem, simply I see routes from switch1 going to hub1
    only if hub1 is not advertising the same routes back, this seems to me a
    perfectly legal split horizon situation, what I'm asking about is why this
    is happening on switch1 instead of any other device and if it can happen
    that this behaviour should migrate to hub1....this way I'll be in big
    troubles.
    I'm not going to disable split horizon since this is a round the clock
    service, what I've tried to do was to fliter the announce for 1 route from
    hub1 to switch1, at this time switch1 started to announce the same route
    back, and only that, to hub1.
    Bye,
    Tosh.
     
    Tosh, Apr 6, 2006
    #31
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