OSPF routing Help

[Ayodeji Okanlawon]

Guys,

I am not a traditional routing and switching guy, I am a core voice specialist. However I have a little project as follows.

I have 4 sites connected via frame-realy.

HQ1, HQ2, SIte a and site b.

The Frame-relay WAN connection is in place and I am using OSPF to do my dynamic routing.

here is my challenge.

HQ1 and HQ2 are in the same LAN, i.e 172.16.1.1 and 172.16.1.2. But in my OSPF database (from sh ip route) I can only see the network for HQ1 been advertised through the HQ1 serial interface. I am using HSRP between HQ1 and HQ2 Lan so that I have resiliency and redundancy. When HQ1 serial goes down, I can nolonger reach the HQ, even though a path is available through HQ2.

Is there a way to make osfp advertise both HQ1 and HQ2 Lan network through different interfaces.? This way when HQ1 serial goes down, I can still reach the 172.16.1.0 network through HQ2.

Many thanks

[Mohamed Sobair]

Hi,

You just need to run OSPF in the LAN segment between HQ1 and HQ2, this way if any of the routers WAN OSPF interfaces fail, other branches would know how to reach both routers.

HTH

Mohamed

[Ayodeji Okanlawon]

Muhammed,

This is exactly what I have done.

Hq1# int fa0/0, ip add 172.16.1.1/24

router ospf 1

network 172.16.1.0 0.0.0.255

hq2#int fa0/0, ip add 172.16.1.2/24

router ospf1

network

network 172.16.1.0 0.0.0.255

However the LAN route is only been advertised through Hq1's serial interface. There is no entry for hq2. Hence when hq1 goes down, the 172.16.1.0 subnet is unreachable

[Mohamed Sobair]

Hi,

This shouldnt be, if both serial Interfaces of both routers HQ1 and HQ2 participate in OSPF, the OSPF database of the branches should include two possible paths to Network 172.16.1.0/24 via HQ1 and HQ2. and the one with the least metric will be installed in the routing table.

If this is the case, Then I would look at my OSPF config on all routers, pleas post your diagram if you have it with the current config so I can look at it.

HTH

Mohamed

[Ayodeji Okanlawon]

Muhammed, here are the relevant configs. Attached is the network diagram.

Muhammed, here are the relevant configs. Attached is the network diagram.

hq1

----------------------

interface FastEthernet0/1

ip address 172.16.1.1 255.255.255.0

duplex auto

speed auto

standby 1 ip 172.16.1.3

standby 1 priority 105

standby 1 preempt

standby 1 track Serial0/2/0

!

interface Serial0/1/0:15

no ip address

isdn switch-type primary-net5

isdn incoming-voice voice

no cdp enable

!

interface Serial0/2/0

ip address 10.2.1.1 255.255.255.0

encapsulation frame-relay

ip ospf network broadcast

ip ospf mtu-ignore

frame-relay map ip 10.2.1.2 711 broadcast  frame-relay map ip 10.2.1.3 710 broadcast  frame-relay map ip 10.2.1.4 712 broadcast  frame-relay lmi-type ansi !

interface Serial0/2/1

no ip address

shutdown

clock rate 2000000

!

router ospf 1

log-adjacency-changes

area 1 virtual-link 172.16.1.1

area 1 virtual-link 10.2.1.1

network 10.2.1.0 0.0.0.255 area 0

network 10.34.255.0 0.0.0.255 area 0

network 172.16.1.0 0.0.0.255 area 0

--

Gateway of last resort is 10.34.255.10 to network 0.0.0.0

     172.16.0.0/24 is subnetted, 2 subnets

C       172.16.1.0 is directly connected, FastEthernet0/1

O       172.16.2.0 [110/65] via 10.2.1.3, 02:07:06, Serial0/2/0

     10.0.0.0/24 is subnetted, 4 subnets

C       10.2.1.0 is directly connected, Serial0/2/0

C       10.66.10.0 is directly connected, FastEthernet0/0.41

O       10.10.101.0 [110/65] via 10.2.1.3, 02:07:06, Serial0/2/0

C       10.34.255.0 is directly connected, FastEthernet0/0.39

O    192.168.1.0/24 [110/65] via 10.2.1.4, 02:07:06, Serial0/2/0

S*   0.0.0.0/0 [1/0] via 10.34.255.10

---------------hq 2--------------------

interface FastEthernet0/0

ip address 172.16.1.2 255.255.255.0

duplex auto

speed auto

standby 1 ip 172.16.1.3

standby 1 priority 110

standby 1 preempt

interface Serial0/0/0

ip address 10.2.1.2 255.255.255.0

encapsulation frame-relay

ip ospf mtu-ignore

no fair-queue

frame-relay traffic-shaping

frame-relay map ip 10.1.2.4 721

frame-relay map ip 10.1.2.3 722

frame-relay map ip 10.1.2.1 720

frame-relay lmi-type ansi

router ospf 1

log-adjacency-changes

network 10.2.1.0 0.0.0.255 area 0

network 172.16.1.0 0.0.0.255 area 0

---------------------------

SITE A when both hq1 and hq 2 wan was up

CCIE-BR1#sh ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-

       ia - IS-IS inter area, * - candidate default, U - per-user static ro

       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     172.16.0.0/24 is subnetted, 2 subnets

O       172.16.1.0 [110/65] via 10.2.1.1, 00:02:16, Serial0/2/0

C       172.16.2.0 is directly connected, FastEthernet0/0

     10.0.0.0/24 is subnetted, 4 subnets

C       10.2.1.0 is directly connected, Serial0/2/0

C       10.10.101.0 is directly connected, FastEthernet0/0.130

C       10.10.201.0 is directly connected, FastEthernet0/0.240

O       10.34.255.0 [110/65] via 10.2.1.1, 00:02:16, Serial0/2/0

O    192.168.1.0/24 [110/65] via 10.2.1.4, 00:02:16, Serial0/2/0

     192.168.100.0/32 is subnetted, 1 subnets

C       192.168.100.3 is directly connected, Loopback0

-------------------------------SITE A sh ip route after int s0/2/0 on hq1 was shut down

Note that the subnet 172.16.1.0 is no longer on the routing table.

CCIE-BR1#sh ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS l

       ia - IS-IS inter area, * - candidate default, U - per-user stat

       o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

     172.16.0.0/24 is subnetted, 1 subnets

C       172.16.2.0 is directly connected, FastEthernet0/0

     10.0.0.0/24 is subnetted, 3 subnets

C       10.2.1.0 is directly connected, Serial0/2/0

C       10.10.101.0 is directly connected, FastEthernet0/0.130

C       10.10.201.0 is directly connected, FastEthernet0/0.240

O    192.168.1.0/24 [110/65] via 10.2.1.4, 00:00:03, Serial0/2/0

     192.168.100.0/32 is subnetted, 1 subnets

C       192.168.100.3 is directly connected, Loopback0

CCIE-BR1#ping 172.16.1.2

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.1.2, timeout is 2 seconds:

.....

Success rate is 0 percent (0/5)

CCIE-BR1#

Note that the subnet 172.16.1.0 is no longer on the routing table.

[Mohamed Sobair · Accepted solution]

Let us now leave HQ1.

Do you have OSPF adjacency between branches and HQ2.   Who is the DR and BDR on this Segment.

Do you have fram relay mapping for HQ2 from the branches as well

Can you post (Sh ip ospf neighbor) from the branches as well as the HQ routers.

Note:

I can see your frame relay is fully meshed Topology with Network as a broadcast type.

HTH

Mohamed

[Ayodeji Okanlawon]

Mohammed,

Thanks for your help. I saw what was wrong. When I issued a sh ip ospf neighbour from the branch sites, I saw that there no neighbour relationship formed to hq2. I observed that the command "ip ospf network broadcast" was missing from the serial interface. Immediately I did this, it worked as expected. When hq1 serial was down, I saw the Lan subnet advertised through hq2. Excellent! Many thanks