Hey you all
I have a very strange problem regarding IS-IS routing process on an ASR903 router, that I hope someone can help me with. I am trying to get IS-IS up and running between an ASR903 router and a ME3600X switch. Between the two boxes is a service provider VPLS network. We have IS-IS running on other similar links between this ASR903 and another ME3600X switch also with a VPLS network between. We are running MPLS in our backbone and uses IS-IS as the underlay IGP. It looks like the two IS-IS routers can’t see each other. When I do a debug of isis adj-packets can I see that the ME3600X switch is sending ISIS hellos packets out but does not receive any in. The same debug on the ASR903 do not give anything. It seems like it not even sending ISIS hellos. Logging level debugging is on. The two boxes can ping each other without any problems.
I have tried a couple of things when troubleshooting this problem. I have tried setting the network type to point-to-point, setting the clns mtu, disabled hello padding but nothing worked. I have also tried running OSPF over the link, and it worked without any problems. Then I tried to make a one-hop gre tunnel between them, and then run IS-IS over the gre tunnel and that also worked. When I issue the “show clns interface” command can I see that the “Next IS-IS LAN Level-2 Hello in” is always 0 on the ASR903 router on that interface. On the others interfaces that is running IS-IS the counter is changing. The same on the interface on the ME3600X switch.The software version on the ASR903 is for the IOS-XE is 3.13.1 and the IOS is 15.4(3).S1.
Do you have any idea’s to what the problem could be?
Solved! Go to Solution.
Here are the show commands :-)
sh run int gi 0/2/1
description INX2-ABC 500Mbps
ip address 10.79.171.142 255.255.255.252
ip router isis
bfd interval 100 min_rx 100 multiplier 3
isis circuit-type level-2-only
isis network point-to-point
isis metric 2000
no isis hello padding
isis bfd disable
sh run | sec router isis
mpls ldp sync
Global CLNS Information:
9 Interfaces Enabled for CLNS
Configuration Timer: 60, Default Holding Timer: 300, Packet Lifetime 64
ERPDU's requested on locally generated packets
Running IS-IS in IP-only mode (CLNS forwarding not allowed)
sh clns interface gi 0/2/1
GigabitEthernet0/2/1 is up, line protocol is up
Checksums enabled, MTU 1497, Encapsulation SAP
ERPDUs enabled, min. interval 10 msec.
CLNS fast switching disabled
CLNS SSE switching disabled
DEC compatibility mode OFF for this interface
Next ESH/ISH in 37 seconds
Routing Protocol: IS-IS
Circuit Type: level-2
Interface number 0x8, local circuit ID 0x103
Level-2 Metric: 2000, Priority: 64, Circuit ID: ASR903-AAL01.03
Level-2 IPv6 Metric: 10
Number of active level-2 adjacencies: 0
Next IS-IS Hello in 0 seconds
No hello padding
if state DOWN
sh ip protocols
*** IP Routing is NSF aware ***
Routing Protocol is "isis"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Maximum path: 4
Routing for Networks:
Routing Information Sources:
Gateway Distance Last Update
100.110.0.19 115 00:02:42
100.110.0.22 115 00:02:42
100.110.0.20 115 00:02:42
100.110.0.21 115 00:02:42
10.79.144.17 115 00:02:42
10.79.144.16 115 00:02:42
10.79.144.15 115 00:02:42
10.79.144.10 115 00:02:42
Distance: (default is 115)
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.79.171.141, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/6/8 ms
I can see the other router in the "show cons nei" on both routers. But under the protocol instead of "is-is" it is "es-is" on both routers (see below).
sh clns nei
System Id Interface SNPA State Holdtime Type Protocol
ME3600-INX02 Gi0/2/1 0c68.03c6.4c59 Up 245 IS ES-IS
I tried to change the clns mtu down to 1400 but it has no effect.
That was the only feature that I forgot to look at. It was a problem with MPLS lDP sync. It was not enable on the interface on the ME3600X switch. After I did that and flap the interfaces the isis neighbor moved to up. Thanks a lot for you help.
I got the same problem on this topic. Now the problem has been solved. Thank you for the action that you reply it.
But I have some question. As per your workaround, I have remove ldp-igp sync on interface for disable this feature then ISIS comes up. But why after isis come up I just enable ldp-igp sync on that interface again (for test) isis not goes down, still seen as isis neighbors.
IGP sync was invented to prevent IGP from coming up before LDP.
As if IGP comes up first (and LDP may be delayed), you would have non-labelled path over the link for some time.
So, IGP sync delays IGP convergence IF you heard LDP hello AND you have route to neighbour's transport address (LDP router-id, typically loopback).
So, here is a case:
The workaround helps you to start IGP and, due to /32 prefix from IGP, LDP converges. But once you reload your box, the same issue would be there.
Solution: don't use static 0.0.0.0/0 (over non-MPLS interface) along with IGP sync or set max delay.