OSPF and MTU issues (between J2320 and Cisco ASR)

[wendohw]

Hi Guys,

I have a JSeries on one side and Cisco Router on the other. Successfully configured OSFP on the two, and all necessary adjacency are UP.

When I do a <show ospf database>  I, can see all routes expected on the Juniper Router, while some are missing on the Cisco side.

When I do a <show ospf interfaces> I can see all required interfaces for OSPF.

Anyone having a clue to such a scenario?

PROBLEM, I cannot see all the Routes on the Cisco, some are missing.

Do I need to do sth on either side to view on both?

Let me know if you need further information.

[chrisp]

Hi,

If you haven't done so already you need to apply an export policy to OSPF on the Juniper router.

For example to export all routes (OSPF, Connected, Direct, etc)

[edit protocols ospf]

export OSPF-EXPORT

[edit policy-options]

policy-statement OSPF-EXPORT {

term acceptable {
then accept;

By default routes are not exported in to OSPF you need to explicity config it.

Hope that helps.

Regards,

Chris

[wendohw]

Hi Chrisp,

Very much appreciated and That makes much sense. Thanks, I will do that tomorrow when I will have a ticket.

I'm just curious, if the MTU's are different on either side, what's the worst that can happen? Or what are the likely behaviours that I will expect between the two routers?

Regards,

[chrisp]

If the MTU's are different the neighbour relationships will never establish.

Regards,

Chris

[rtrabelsi]

you don t need an explicit export policy to advertise ospf route unless you actually distributing static or direct or other protocol into ospf. 

[wendohw]

Hi rt,

So, what do you suggest? I will be on site tomorrow.

[B2]

You say that the Cisco side is missing some LSAs that you think should be advertised from the Juniper.  That tends to indicate to me that OSPF maybe isn't activated on all the links on the Juniper that you intended, but you do state that 'show ospf interfaces' lists all appropriate interfaces.  Could you post the Juniper OSPF config, and maybe describe which LSAs you think should be in the database of the Cisco and are not?  Showing the OSPF databases on the Juniper and Cisco side would be helpful as well.

[wendohw]

Hi B2, here are my current configs.

On the Juniper side (j2320).

 ge-0/0/3 {
        description "ISP LINK to BRANCH";
        mtu 1500;
        unit 0 {
            description "ISP to BRANCH";
            family inet {
                address 10.206.125.45/30;
            }
        }
    }
    lo0 {
        unit 0 {
            family inet {
                address 10.206.119.130/30;
            }
        }
    }
}

routing-options {
    static {
        route 0.0.0.0/0 next-hop 10.206.125.46;  //HQ side cisco-IP on other side
    }
    router-id 10.206.125.45;
}
protocols {
    ospf {
        area 0.0.0.0 {
            area-range 10.206.35.0/24;
            area-range 10.206.125.44/30;
            area-range 10.206.119.130/32;
            network-summary-export ospf-default;
            network-summary-import ospf-default;
            interface ge-0/0/3.0 {
                metric 2000;
            }
            interface lo0.0;
        }
    }
    lldp {
        interface all;
    }
    lldp-med {
        interface all;
    }
}
policy-options {
    policy-statement ospf-default {
        from {
            protocol static;
            route-filter 0.0.0.0/0 exact;
        }
        then accept;
    }
}

Then, on the Cisco Side. (OSPF and interfaces).

!
interface FastEthernet0/0/1.34
 description HQ to XXX- BRANCH : 256K - PRI ISP-LINK
 encapsulation dot1Q 640
 ip address 10.206.125.46 255.255.255.252
 ip mtu 1486
 ip flow ingress
 ip flow egress
 ip ospf network point-to-point
 ip ospf cost 2000
 no cdp enable
end


ip forward-protocol nd
ip route 10.206.35.0 255.255.255.0 10.206.125.45
no ip http server

router ospf 100
 log-adjacency-changes
 redistribute static subnets
 network 10.206.125.44 0.0.0.3 area 0

Problem: On the cisco side, although the OSPF ADJ forms in FULL, I cannot see a route/neighbor to the Juniper Neighbor. I use this command on cisco to check "show ip ospf interface " to check!

NB: Adjacency is FULL on both sides and "show ip ospf neighbor" is working fine, as it shows the neighbor.

[jtb]

hi all,

the topology (single OSPF link between Juniper and Cisco) seems to be simple. The OSPF configuration on J2320 is bizarre:

• interfaces ge-0/0/3.0 & lo0.0 added - good
• what's the point with area-range and network-summary-export/import  ? What do you want to achieve ?

Please describe the expected network behavior and show results of commands (both sides; convert commands to IOS version):

• show ospf neighbor detail
• show ospf interface detail
• show ospf database

I really doubt you have OSPF adjacency with ip mtu 1486 and ip ospf network point-to-point on Cisco side. Please

keep the MTU equal and the same OSPF network type on both sides (simple way  is to remove both commands on Cisco).

MTU size must be equal or LSDB exchange will stuck in Exstart/Exchange (http://kb.juniper.net/InfoCenter/index?page=content&id=KB1352)

J2320 interface is configured as OSPF type LAN (default), Cisco is p2p - another obstacle for OSPF.

jtb