Re: ODDITY - OSPF E2 preferred above E1

It's kind of hard to be sure as there appears to be information
missing/incorrect below BUT if an E1 route is being learned across the
MPLS "super backbone" then that means its probably, assuming no SHAM link,
in the PE's RIB as iBGP which has an admin distance of 200. This iBGP
route is then redistributed into OSPF as an E1. If the E2 route is
learned via OSPF by the same PE it will have an admin distance of 110.
This would overtake the iBGP route and in turn would stop the E1 from
being redistributed into OSPF on the PE.

Also in your case below the OSPF route from R4 (PE) isn't an E1 but an E2:

Routing Bit Set on this LSA
  LS age: 55
  Options: (No TOS-capability, DC)
  LS Type: AS External Link
  Link State ID: 12.12.12.12 (External Network Number )
  Advertising Router: 0.0.0.4
  LS Seq Number: 80000001
  Checksum: 0xF046
  Length: 36
  Network Mask: /32
        Metric Type: 2 (Larger than any link state path) <--- E2
        TOS: 0
        Metric: 20
        Forward Address: 0.0.0.0
        External Route Tag: 3489661028

-- 
Brian Dennis, CCIEx5 #2210 (R&S/ISP-Dial/Security/SP/Voice)
bdennis_at_ine.com
INE, Inc.
http://www.INE.com 
On 4/11/13 2:03 PM, "bitje" <lj_at_cli.nu> wrote:
>Hi,
>
>I have a situation where a E1 route is being overriden by a E2 route.
>The E1 route is entering the area from a mpls superbackbone and the
>E2 from an ASBR in the same area. According to what I know an E1
>route should always win from a E2 route.. I feel that I am going
>to learn something here.
>
>R5 is connected to SW2 and R4.
>
>On SW2 the following is done:
>!
>ip route 12.12.12.12 255.255.255.255 Null0
>!
>router ospf 100
> router-id 0.0.0.8
> log-adjacency-changes
> redistribute static subnets
> network 155.1.58.8 0.0.0.0 area 0
>!
>
>On R4 the following is done:
>!
>router ospf 100 vrf TEST
> router-id 0.0.0.4
> log-adjacency-changes
> redistribute bgp 100 subnets
> network 155.1.45.4 0.0.0.0 area 0
>!
>router bgp 100
> no synchronization
> bgp log-neighbor-changes
> neighbor 6.6.6.6 remote-as 100
> neighbor 6.6.6.6 update-source Loopback10
> neighbor 204.12.1.254 remote-as 54
> no auto-summary
> !
> address-family vpnv4
>  neighbor 6.6.6.6 activate
>  neighbor 6.6.6.6 send-community extended
> exit-address-family
> !
> address-family ipv4 vrf TEST
>  no synchronization
> exit-address-family
>!
>
>On R5 the following is done:
>!
>router ospf 100
> router-id 0.0.0.5
> log-adjacency-changes
> network 155.1.45.5 0.0.0.0 area 0
> network 155.1.58.5 0.0.0.0 area 0
>Rack1R5#
>
>Some relevant show commands:
>
>Rack1R5#show ip route ospf 100
>     12.0.0.0/32 is subnetted, 1 subnets
>O E2    12.12.12.12 [110/20] via 155.1.58.8, 05:41:13, FastEthernet0/0
>Rack1R5#
>
>Rack1R5#show ip ospf database external 12.12.12.12
>
>            OSPF Router with ID (0.0.0.5) (Process ID 100)
>
>		Type-5 AS External Link States
>
>  Routing Bit Set on this LSA
>  LS age: 1494
>  Options: (No TOS-capability, DC)
>  LS Type: AS External Link
>  Link State ID: 12.12.12.12 (External Network Number )
>  Advertising Router: 0.0.0.8
>  LS Seq Number: 8000000B
>  Checksum: 0x79E4
>  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
>
>Rack1R5#
>
>Rack1R5#show ip ospf database router 0.0.0.8
>
>            OSPF Router with ID (0.0.0.5) (Process ID 100)
>
>		Router Link States (Area 0)
>
>  Routing Bit Set on this LSA
>  LS age: 1533
>  Options: (No TOS-capability, DC)
>  LS Type: Router Links
>  Link State ID: 0.0.0.8
>  Advertising Router: 0.0.0.8
>  LS Seq Number: 80000024
>  Checksum: 0xDF9B
>  Length: 36
>  AS Boundary Router
>  Number of Links: 1
>
>    Link connected to: a Transit Network
>     (Link ID) Designated Router address: 155.1.58.5
>     (Link Data) Router Interface address: 155.1.58.8
>      Number of TOS metrics: 0
>       TOS 0 Metrics: 200
>
>          
>Rack1R5#
>
>Now if I remove the static route on SW2:
>Rack1SW2(config)#no ip route 12.12.12.12 255.255.255.255 Null0
>
>And ask R5 what external route it has we see that only after
>the static from SW2 has been removed R5 will accept the E1
>route since the E2 route is no longer available:
>
>Rack1R5#show ip ospf database external
>
>            OSPF Router with ID (0.0.0.5) (Process ID 100)
>
>		Type-5 AS External Link States
>
>  Routing Bit Set on this LSA
>  LS age: 55
>  Options: (No TOS-capability, DC)
>  LS Type: AS External Link
>  Link State ID: 12.12.12.12 (External Network Number )
>  Advertising Router: 0.0.0.4
>  LS Seq Number: 80000001
>  Checksum: 0xF046
>  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: 3489661028
>
>Rack1R5#
>
>Rack1R5#show ip ospf database router 0.0.0.4
>
>            OSPF Router with ID (0.0.0.5) (Process ID 100)
>
>		Router Link States (Area 0)
>
>  Routing Bit Set on this LSA
>  LS age: 820
>  Options: (No TOS-capability, DC)
>  LS Type: Router Links
>  Link State ID: 0.0.0.4
>  Advertising Router: 0.0.0.4
>  LS Seq Number: 80000016
>  Checksum: 0xAB3C
>  Length: 48
>  Area Border Router
>  AS Boundary Router
>  Number of Links: 2
>
>    Link connected to: another Router (point-to-point)
>     (Link ID) Neighboring Router ID: 0.0.0.5
>     (Link Data) Router Interface address: 155.1.45.4
>      Number of TOS metrics: 0
>       TOS 0 Metrics: 64
>          
>    Link connected to: a Stub Network
>     (Link ID) Network/subnet number: 155.1.45.0
>     (Link Data) Network Mask: 255.255.255.0
>      Number of TOS metrics: 0
>       TOS 0 Metrics: 64
>
>
>Rack1R5#
>
>Your analysis/help is appreciated.
>
>Regards
>
>
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