From: Chris Lewis (chrlewiscsco@gmail.com)
Date: Fri Mar 10 2006 - 13:57:55 GMT-3
Yes.
This is a corner case only for BGP, OSPF and synchronisation turned on.
show ip ospf data will give you the router ID used by each OSPF speaker.
show ip bgp will give you the router id used by BGP.
show ip ospf data router for example will show you the advertising router ID
of the router link state LSAs. show ip bgp A.B.C.D will show you the BGP
router ID of the BGP speaker originating the route.
In the corner case described above, the router ID of the OSPF originator and
the BGP originator have to match for the route to be installed in the
routing table.
Chris
On 3/10/06, san <san.study@gmail.com> wrote:
>
> Chris,
>
> Basic question, based on your explanation. I have pasted sh commands.
> By saying Router-id...I think you are trying to mean "advertising
> router field". correct ?
>
> Also, How would i change the advertising router or Router-id ? Any
> method or commands ?
>
>
> Rack1R2#sh ip ospf database
>
> OSPF Router with ID (12.12.12.12) (Process ID 12)
>
> Router Link States (Area 12)
>
> Link ID ADV Router Age Seq# Checksum Link count
> 11.11.11.11 11.11.11.11 879 0x800000E0 0x00E1FC 1
> 12.12.12.12 12.12.12.12 1108 0x800000DD 0x00C314 1
> 13.13.13.13 13.13.13.13 868 0x800000DF 0x005848 2
>
> Net Link States (Area 12)
>
> Link ID ADV Router Age Seq# Checksum
> 10.1.1.1 11.11.11.11 879 0x800000DC 0x00FCC7
> 10.1.2.2 12.12.12.12 1108 0x800000DA 0x00EFCC
>
> Type-5 AS External Link States
>
> Link ID ADV Router Age Seq# Checksum Tag
> 10.1.0.0 11.11.11.11 1011 0x80000001 0x000E5B 0
> 111.111.111.111 11.11.11.11 1012 0x80000001 0x009620 0
> Rack1R2#
> Rack1R2#
> Rack1R2#sh ip ospf data
> Rack1R2#sh ip ospf database external
>
> OSPF Router with ID (12.12.12.12) (Process ID 12)
>
> Type-5 AS External Link States
>
> Routing Bit Set on this LSA
> LS age: 1084
> Options: (No TOS-capability, DC)
> LS Type: AS External Link
> Link State ID: 10.1.0.0 (External Network Number )
> Advertising Router: 11.11.11.11
> LS Seq Number: 80000001
> Checksum: 0xE5B
> Length: 36
> Network Mask: /16
> Metric Type: 2 (Larger than any link state path)
> TOS: 0
> Metric: 20
> Forward Address: 0.0.0.0
> External Route Tag: 0
>
> Routing Bit Set on this LSA
> LS age: 1085
> Options: (No TOS-capability, DC)
> LS Type: AS External Link
> Link State ID: 111.111.111.111 (External Network Number )
> Advertising Router: 11.11.11.11
> LS Seq Number: 80000001
> Checksum: 0x9620
> Length: 36
> Network Mask: /32
> Metric Type: 2 (Larger than any link state path)
> TOS: 0
> Metric: 20
> Forward Address: 0.0.0.0
> External Route Tag: 0
>
>
> Thanks
> SAN
>
> On 3/9/06, Chris Lewis <chrlewiscsco@gmail.com> wrote:
> > When I did this the extra step for OSPF of checking the router ID of the
> > OSPF supplied prefix (sho ip ospf databse) and the router ID of the BGP
> > route (sho ip bgp a.b.c.d) matched.
> >
> > If the OSPF route is originated on one router, then brought in to BGP on
> > another, the router IDs of the prefixes will not match between these two
> > protocols and therefore won't be installed by BGP. On your config it
> looks
> > to me like OSPF originates 20.20.20.20 on SW2 and it is brought in to
> BGP on
> > R2, so the router IDs of the prefixes (who originated them) will not
> match
> > and therefore the prefixes fail this additional BGP/OSPF check.
> >
> > Chris
> >
> >
> > On 3/8/06, Mushtaq A. Khan <mak.ccie2b@gmail.com> wrote:
> > >
> > >
> > > As I mentioned previously in my email I was able to complete this
> > > requirement using BGP Confederation but in order to do this I had to
> > > configure 3 new ASs (65001, 65002, 65003) which were mentioned in the
> > > requiment. My question is that are we allowed to do this in the lab
> exam.
> > > Aren't configuring something that is not asked? Can someone comment on
> > this?
> > > Also, it would be very helpful if someone give me a tip to get this
> > > requirement done using route-reflector option with Synchronization
> enable
> > > for AS100.
> > >
> > > Thanks,
> > > Mushtaq
> > >
> > > On 3/8/06, Mushtaq A. Khan <mak.ccie2b@gmail.com> wrote:
> > > >
> > > > Chris,
> > > >
> > > > Yes, both BGP and OSPF router-ids matches.
> > > >
> > > > Mushtaq
> > > >
> > > >
> > > > On 3/8/06, Chris Lewis <chrlewiscsco@gmail.com > wrote:
> > > > >
> > > > > For the routes in question, does teh OSPF router ID match the BGP
> > > > > router ID?
> > > > >
> > > > > Chris
> > > > >
> > > > >
> > > > > On 3/8/06, Mushtaq A. Khan <mak.ccie2b@gmail.com > wrote:
> > > > > >
> > > > > > Nick,
> > > > > >
> > > > > > Thanks for the tip but if you notice in my configuration I have
> > > > > > already
> > > > > > redistributed BGP into IGP in their respective peer routers in
> AS100
> > > > > > to put
> > > > > > these prefixes in the route table. When I checked the routes
> table
> > > > > > all three
> > > > > > routes shows there as well but this is still not working.
> > > > > >
> > > > > > Mushtaq
> > > > > >
> > > > > >
> > > > > > On 3/8/06, Popgeorgiev Nikolay < nikolay.popgeorgiev@siemens.com
> >
> > > > > > wrote:
> > > > > > >
> > > > > > > Dear Mushtaq,
> > > > > > >
> > > > > > >
> > > > > > > I didn't go really through all your post but I can tell you
> how I
> > > > > > did this
> > > > > > > thing and what problems I faced in a similar task:
> > > > > > >
> > > > > > > I used RR in AS 100, R1 as a route reflector and R2 as its
> client.
> > > > > > > Because the requirement says do't disable synchronization, in
> > > > > > order for R1
> > > > > > > for example to put network 20.20.20.20 into its routing table,
> it
> > > > > > has to
> > > > > > > have this route known already via IGP or static or connected.
> > > > > > > So my solution is to redistribute BGP into IGP on router R2.
> This
> > > > > > is not a
> > > > > > > very clever thing to do if you have many routes coming from
> BGP
> > > > > > but in this
> > > > > > > case helps :)
> > > > > > >
> > > > > > >
> > > > > > > Try it and if I have missed something in your explanations
> sorry
> > > > > > about
> > > > > > > that
> > > > > > >
> > > > > > > Best,
> > > > > > > Nick
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: Mushtaq A. Khan [mailto:mak.ccie2b@gmail.com]
> > > > > > > Sent: Wednesday, March 08, 2006 7:59 AM
> > > > > > > To: ccielab@groupstudy.com
> > > > > > > Subject: EBGP peer is not advertising prefixes from other EBGP
> > > > > > peer while
> > > > > > > synchronization is enabled in Transit ASs
> > > > > > >
> > > > > > > Hi Team,
> > > > > > >
> > > > > > > I have a scenario as shown below.
> > > > > > >
> > > > > > > SW2(AS200) ----(RIP)-----R2(AS100)
> > > > > > > \
> > > > > > > (OSPF)
> > > > > > > \
> > > > > > >
> R1(AS100)
> > > > > > > -----(OSPF)----R6(AS600)
> > > > > > > /
> > > > > > > (OSPF)
> > > > > > > /
> > > > > > > R5(AS600)-----EIGRP-----R3(AS100)
> > > > > > >
> > > > > > > The task is to advertise the following prefixes in BGP ONLY
> within
> > > > > > their
> > > > > > > respective ASs and these should be exchanged between all AS's.
> > > > > > >
> > > > > > > 20.20.20.20(SW2)
> > > > > > > 5.5.5.5 (R5)
> > > > > > > 6.6.6.6 (R6)
> > > > > > >
> > > > > > > AS100 should provide transit path between the above prefixes
> and
> > > > > > MUST not
> > > > > > > disable synchronization and use minimal number of BGP
> speakers.
> > > > > > >
> > > > > > > One solution to above requirement is to use BGP confederation
> > > > > > within
> > > > > > > AS100.
> > > > > > > I tried to solve this using route reflector and facing
> difficulty:
> > > > > > I
> > > > > > > noticed
> > > > > > > R6 is able to see all 3 prefixes in its BGP table. However, R5
> and
> > > > > > SW2
>
>
> > > > > > > can't
> > > > > > > see each other prefixes. I tried different options but with no
> > > > > > luck.
> > > > > > > Anyone
> > > > > > > has any clue to resolve this issue here.
> > > > > > >
> > > > > > > All relevent configuration are given below:
> > > > > > >
> > > > > > > R2#sh run | beg router bgp
> > > > > > > router bgp 100
> > > > > > > synchronization
> > > > > > > bgp log-neighbor-changes
> > > > > > > neighbor 172.16.20.10 remote-as 200
> > > > > > > neighbor 172.16.101.1 remote-as 100
> > > > > > > neighbor 172.16.101.1 update-source Loopback102
> > > > > > > no auto-summary
> > > > > > > !
> > > > > > > R2#sh run | beg router ospf|route-map
> > > > > > > router ospf 1
> > > > > > > log-adjacency-changes
> > > > > > > redistribute rip subnets
> > > > > > > redistribute bgp 100 subnets route-map BGPtoOSPF
> > > > > > > network 172.16.102.1 0.0.0.0 area 20
> > > > > > > network 172.16.123.2 0.0.0.0 area 0
> > > > > > > !
> > > > > > > ip prefix-list BGP-Route seq 5 permit 20.20.20.0/24
> > > > > > > !
> > > > > > > route-map BGPtoOSPF permit 10
> > > > > > > match ip address prefix-list BGP-Route
> > > > > > >
> > > > > > > R2#sh ip bgp | beg Network
> > > > > > > Network Next Hop Metric LocPrf Weight
> Path
> > > > > > > * i5.5.5.0/24 172.16.35.5 0 100 0
> 500 i
> > > > > > > r>i6.6.6.0/24 172.16.16.6 0 100 0
> 600 i
> > > > > >
> > > > > > > *> 20.20.20.0/24 172.16.20.10 0 0
> 200
> > > > > > i
> > > > > > >
> > > > > > > sw2#sh ip bgp | beg Network
> > > > > > > Network Next Hop Metric LocPrf Weight
> Path
> > > > > > > *> 6.6.6.0/24 172.16.20.2 0
> 100
> > > > > > 600 i
> > > > > > > *> 20.20.20.0/24 0.0.0.0 0 32768
> i
> > > > > > >
> > > > > > > R1#sh run | beg router ospf|route-map
> > > > > > > router ospf 1
> > > > > > > router-id 172.16.101.1
> > > > > > > redistribute bgp 100 subnets route-map BGPtoOSPF
> > > > > > > !
> > > > > > > router bgp 100
> > > > > > > synchronization
> > > > > > > bgp log-neighbor-changes
> > > > > > > neighbor AS100 peer-group
> > > > > > > neighbor AS100 remote-as 100
> > > > > > > neighbor AS100 update-source Loopback101
> > > > > > > neighbor AS100 route-reflector-client
> > > > > > > neighbor 172.16.16.6 remote-as 600
> > > > > > > neighbor 172.16.102.1 peer-group AS100
> > > > > > > neighbor 172.16.103.1 peer-group AS100
> > > > > > > no auto-summary
> > > > > > > !
> > > > > > > !
> > > > > > > ip prefix-list BGP-Routes seq 5 permit 6.6.6.0/24
> > > > > > > !
> > > > > > > route-map BGPtoOSPF permit 10
> > > > > > > match ip address prefix-list BGP-Routes
> > > > > > > !
> > > > > > >
> > > > > > > R1#sh ip bgp | beg Network
> > > > > > > Network Next Hop Metric LocPrf Weight
> Path
> > > > > > > r>i5.5.5.0/24 172.16.35.5 0 100 0
> 500 i
> > > > > >
> > > > > > > *> 6.6.6.0/24 172.16.16.6 0 0
> 600 i
> > > > > > > r>i20.20.20.0/24 172.16.20.10 0 100 0
> 200
> > > > > > i
> > > > > > >
> > > > > > > R6#sh ip bgp | beg Network
> > > > > > > Network Next Hop Metric LocPrf Weight
> Path
> > > > > > > *> 5.5.5.0/24 172.16.16.1 0
> 100
> > > > > > 500 i
> > > > > > > *> 6.6.6.0/24 0.0.0.0 0 32768 i
> > > > > > > *> 20.20.20.0/24 172.16.16.1 0
> 100
> > > > > > 200 i
> > > > > > >
> > > > > > > R3#sh run | beg router ospf|route-map
> > > > > > > router ospf 1
> > > > > > > log-adjacency-changes
> > > > > > > redistribute bgp 100 subnets route-map BGPtoOSPF
> > > > > > >
> > > > > > >
> > > > > > > router bgp 100
> > > > > > > synchronization
> > > > > > > bgp log-neighbor-changes
> > > > > > > neighbor 172.16.35.5 remote-as 500
> > > > > > > neighbor 172.16.101.1 remote-as 100
> > > > > > > neighbor 172.16.101.1 update-source Loopback103
> > > > > > > no auto-summary
> > > > > > > !
> > > > > > >
> > > > > > > !
> > > > > > > ip prefix-list BGP-Routes seq 5 permit 5.5.5.0/24
> > > > > > > !
> > > > > > > route-map BGPtoOSPF permit 10
> > > > > > > match ip address prefix-list BGP-Routes
> > > > > > >
> > > > > > > R3#sh ip bgp | beg Network
> > > > > > > Network Next Hop Metric LocPrf Weight
> Path
> > > > > > > *> 5.5.5.0/24 172.16.35.5 0 0
> 500 i
> > > > > > > r>i6.6.6.0/24 172.16.16.6 0 100 0
> 600 i
> > > > > >
> > > > > > > * i20.20.20.0/24 172.16.20.10 0 100 0
> 200 i
> > > > > >
> > > > > > > R3#
> > > > > > > R5#sh ip bgp | beg Network
> > > > > > > Network Next Hop Metric LocPrf Weight
> Path
> > > > > > > *> 5.5.5.0/24 0.0.0.0 0 32768 i
> > > > > > > *> 6.6.6.0/24 172.16.35.3 0
> 100
> > > > > > 600 i
> > > > > > >
> > > > > > > TIA,
> > > > > > > Mushtaq
> > > > > > >
> > > > > > >
> > > > > >
> > _______________________________________________________________________
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> >
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