set the mtu back to default

ssweehinlew · ‎02-26-2015

I try to setup the simple OSPF connection between 2 switches. The setup was done and the protocol is running. When I do the tracertroute from workstation 172.21.6.1 to the next 2 hop of the IP 172.21.3.1, it cannot reach it. It stop at the gateway 172.21.6.254.

Any items I miss out and does static route need to be added?

SW1(config)#router ospf 1
SW1(config-router)#network 172.21.3.0 0.0.0.255 area 2
SW1(config-router)#network 1.1.1.0 0.0.0.255 area 2
SW1(config-router)#network 10.1.3.0 0.0.0.255 area 2

SW2(config)#router ospf 1
SW2(config-router)#network 172.21.6.0 0.0.0.255 area 2
SW2(config-router)#network 2.2.2.0 0.0.0.255 area 2
SW2(config-router)#network 172.21.3.0 0.0.0.255 area 2

Reza Sharifi · ‎02-26-2015

You need to have common subnet between the 2 switches in order for the peering to work correctly

lets assume int gi0/1 on switch-1 and gi0/1 on switch-2 are connecting the switches together

You need a config like this for each interface

switch-1

config t

int gi0/1

ip add 172.21.3.1 255.255.255.0

no sh

router ospf 1

network 172.21.3.0 0.0.0.255 area 0

switch-2

config t

int gi0/1

ip add 172.21.3.2 255.255.255.0

no sh

router ospf 1

network 172.21.3.0 0.0.0.255 area 0

verify with "sh ip os nei" the switches are neighbors

HTH

ssweehinlew · ‎02-27-2015

Let me try it out first.

paul driver · ‎02-27-2015

Hello

Can you ping the neighbour, is so can you do it with also with a large mtu size specified?

Debug ip ospf adj

res

Paul

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Paul

ssweehinlew · ‎03-01-2015

Hi,

Please refer to below. I have no problem to ping the interface from both of the switches. Can I know confirm that no static route is required for this setup in order for sw1 to ping to sw2 loopback interface?

Switch#debug ip ospf adj
OSPF adjacency events debugging is on
Switch#
00:04:34: OSPF: Rcv DBD from 2.2.2.2 on Vlan506 seq 0x20BCFF9 opt 0x52 flag 0x7 len 32 mtu 1500 state EXCHANGE
00:04:34: OSPF: Nbr 2.2.2.2 has smaller interface MTU
00:04:34: OSPF: Send DBD to 2.2.2.2 on Vlan506 seq 0x20BCFF9 opt 0x52 flag 0x2 len 52
00:04:38: OSPF: Rcv DBD from 2.2.2.2 on Vlan506 seq 0x20BCFF9 opt 0x52 flag 0x7 len 32 mtu 1500 state EXCHANGE
00:04:38: OSPF: Nbr 2.2.2.2 has smaller interface MTU
00:04:38: OSPF: Send DBD to 2.2.2.2 on Vlan506 seq 0x20BCFF9 opt 0x52 flag 0x2 len 52
00:04:43: OSPF: Rcv DBD from 2.2.2.2 on Vlan506 seq 0x20BCFF9 opt 0x52 flag 0x7 len 32 mtu 1500 state EXCHANGE
00:04:43: OSPF: Nbr 2.2.2.2 has smaller interface MTU
00:04:43: OSPF: Send DBD to 2.2.2.2 on Vlan506 seq 0x20BCFF9 opt 0x52 flag 0x2 len 52

paul driver · ‎03-02-2015

Hello

On the switch interface running ip ospf

int x/x
ip ospf ignore-mtu

res

Paul

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Paul

ssweehinlew · ‎03-02-2015

After i issue the ip ospf mtu-ignore, i do not see the message "00:04:34: OSPF: Nbr 2.2.2.2 has smaller interface MTU" come out from debug log.

I still have one question about it. Does static route is required for this setup in order for sw1 to ping to sw2 loopback interface and vice versa?

paul driver · ‎03-03-2015

Hello

I am a bit confused now as to how your topology is set up, Can you post a diagram and running config of your switches please

res

Paul

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ssweehinlew · ‎03-13-2015

The connection is just between 2 switches.

Below configuration indicated the network advertises the route to each other from both switches. Does static route is required?

SW1(config)#router ospf 1
SW1(config-router)#network 172.21.3.0 0.0.0.255 area 2
SW1(config-router)#network 1.1.1.0 0.0.0.255 area 2
SW1(config-router)#network 10.1.3.0 0.0.0.255 area 2

SW2(config)#router ospf 1
SW2(config-router)#network 172.21.6.0 0.0.0.255 area 2
SW2(config-router)#network 2.2.2.0 0.0.0.255 area 2
SW2(config-router)#network 172.21.3.0 0.0.0.255 area 2

Jon Marshall · ‎03-13-2015

No, you should not need a static route if OSPF is running and exchanging routes properly.

Are you saying it is not working ?

Jon

ssweehinlew · ‎03-13-2015

Yes. It is not working until I added in the static route. I wonder how come like that..

Jon Marshall · ‎03-13-2015

Can you draw a quick diagram showing the IPs of the switch connections and where the PCs are ?

What do the routing tables look like on each switch ?

Jon

Andrew.C11 · ‎03-15-2015

set the mtu back to default 1500 (on both routers)

interface xxx
no ip mtu

ssweehinlew · ‎03-15-2015

Please refer to the attached diagram

ssweehinlew · ‎03-16-2015

Please refer to below:

SW1 (Cisco)
-------

Switch#sh ip ospf database

OSPF Router with ID (1.1.1.1) (Process ID 10)

Router Link States (Area 2)

Link ID ADV Router Age Seq# Checksum Link count
1.1.1.1 1.1.1.1 357 0x80000003 0x000D20 3

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag
0.0.0.0 1.1.1.1 467 0x80000001 0x00BFE5 10
Switch#sh ip ospf interface brief
Interface PID Area IP Address/Mask Cost State Nbrs F/C
Vl506 10 2 172.21.3.1/24 1 BDR 0/1
Fa0/2 10 2 10.1.3.253/24 1 DR 0/0
Lo0 10 2 1.1.1.1/32 1 LOOP 0/0
Switch#sh ip ospf nei

Neighbor ID Pri State Dead Time Address Interface
2.2.2.2 128 EXCHANGE/DR 00:00:39 172.21.3.2 Vlan506

Switch#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-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1 is directly connected, Loopback0
2.0.0.0/32 is subnetted, 1 subnets
S 2.2.2.2 [1/0] via 172.21.3.2
172.21.0.0/24 is subnetted, 1 subnets
C 172.21.3.0 is directly connected, Vlan506
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.3.0 is directly connected, FastEthernet0/2

Sw2 (Juniper)
-------

root> show ospf database

OSPF database, Area 0.0.0.2
Type ID Adv Rtr Seq Age Opt Cksum Len
Router *2.2.2.2 2.2.2.2 0x80000008 838 0x22 0xb896 72

root> show ospf interface
Interface State Area DR ID BDR ID Nbrs
lo0.0 DR 0.0.0.2 2.2.2.2 0.0.0.0 0
vlan.0 DR 0.0.0.2 2.2.2.2 1.1.1.1 1
vlan.702 DR 0.0.0.2 2.2.2.2 0.0.0.0 0

root> show ospf neighbor
Address Interface State ID Pri Dead
172.21.3.1 vlan.0 ExStart 1.1.1.1 1 36

root> show route

inet.0: 8 destinations, 8 routes (8 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

2.2.2.0/24 *[Direct/0] 00:16:35
> via lo0.0
2.2.2.2/32 *[Local/0] 00:16:35
Local via lo0.0
172.21.3.0/24 *[Direct/0] 00:16:29
> via vlan.0
172.21.3.2/32 *[Local/0] 00:16:35
Local via vlan.0
172.21.6.0/24 *[Direct/0] 00:16:23
> via vlan.702
172.21.6.254/32 *[Local/0] 00:16:34
Local via vlan.702
224.0.0.5/32 *[OSPF/10] 00:16:40, metric 1
MultiRecv
224.0.0.22/32 *[IGMP/0] 00:16:39
MultiRecv

Traceroute from user pC

C:\Users\admin>ping 172.21.6.254

Pinging 172.21.6.254 with 32 bytes of data:
Reply from 172.21.6.254: bytes=32 time=1ms TTL=64

Ping statistics for 172.21.6.254:
Packets: Sent = 1, Received = 1, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 1ms, Maximum = 1ms, Average = 1ms
Control-C
^C
C:\Users\admin>tracert -d 172.21.3.1

Tracing route to 172.21.3.1 over a maximum of 30 hops

1 1 ms 3 ms 1 ms 172.21.6.254
2 * *

OSPF configuration