Re: ISIS Issue between XR and IOS

Debug isis adjacency on IOS device it should complain about the MTU padding being received as 4 bytes less than what the interface should support end result in no peering.

1497 bytes minus 3 byte LLC encapsulation, IOS device not like 1493 bytes seems the dot1q tag add overhead before being discarded..

To disable the check

IOS
router isis
no hello padding
Or
int f0/0.100
no isis hello padding

IOS-XR
router isis abc
 interface GigabitEthernet0/0/0/0.100
  no hello-padding disable level [1/2]

Design reason for this check is that no issues are encountered at a later stage with LSP packet exchange.

In IOS & XR you can run a more intuitive check like the Junos implementation where padding is only checked upon adjacency thereafter it doesn't bother thus saving bandwidth too, can you imagine SONET HDLC with an MTU of 4470 consistently sending hellos

--
BR
Tony
> On 7 Jun 2014, at 06:20, GAURAV MADAN <gauravmadan1177_at_gmail.com> wrote:
> 
> I believe that is mandatory . (but i can double check as well)
> ISIS works smooth b/w IOS and XR for me till now and i have made it a best
> practice to activate address-family on global as well as interface level .[
> more or less like bgp ]
> 
> 
>> On 7 June 2014 10:30, Rakesh M <raaki.88_at_gmail.com> wrote:
>> 
>> i dont think that is the requirement Gaurav, anyways i have even tried
>> that, must be a hardware issue , tried on INE labs and it works fine with
>> the same configuration, virtualisation has its own impact on time ! :)
>> 
>> Below is from INE lab
>> 
>> router isis 1
>> 
>> net 49.0001.0000.0000.0020.00
>> interface Loopback0
>>  passive
>>  address-family ipv4 unicast
>>  !
>> !
>> interface GigabitEthernet0/4/0/0.620
>> 
>>  address-family ipv4 unicast
>>  !
>> !
>> !
>> 
>> RP/0/3/CPU0:XR2#show isis neighbors
>> Wed Oct 25 11:36:33.610 UTC
>> 
>> IS-IS 1 neighbors:
>> System Id      Interface        SNPA           State Holdtime Type IETF-NSF
>> R6             Gi0/4/0/0.620    0004.4e11.2800 Up    7        L1L2 Capable
>> 
>> 
>> On Sat, Jun 7, 2014 at 10:10 AM, GAURAV MADAN <gauravmadan1177_at_gmail.com>
>> wrote:
>> 
>>> on XR ; you have not activated the address-family on protocol level . You
>>> have just activated under interface. Please correct the same
>>> 
>>> 
>>>> On 7 June 2014 08:23, Rakesh M <raaki.88_at_gmail.com> wrote:
>>>> 
>>>> Hi,
>>>> 
>>>> I am trying to run isis between IOS-XRV 5.3.2 and Cisco 7600 Series, Both
>>>> are emulated
>>>> version for FYI.
>>>> 
>>>> ospf appears to form fine, and IOS-TO-IOS ISIS is also fine, I am unable
>>>> to
>>>> relate
>>>> why XR-IOS isis-adj is not coming up.
>>>> 
>>>> !
>>>> router isis 1
>>>> net 49.0001.0000.0000.0006.00
>>>> is-type level-2-only
>>>> !
>>>> 
>>>> R6#
>>>> R6#show runn int fa0/0.620
>>>> Building configuration...
>>>> 
>>>> Current configuration : 182 bytes
>>>> !
>>>> interface FastEthernet0/0.620
>>>> encapsulation dot1Q 620
>>>> ip address 20.6.20.6 255.255.255.0
>>>> ip router isis 1
>>>> mpls ip
>>>> mpls label protocol ldp
>>>> isis circuit-type level-2-only
>>>> end
>>>> 
>>>> 
>>>> *Jun  7 08:21:11.159: ISIS-Adj: Sending L2 LAN IIH on
>>>> FastEthernet0/0.620,
>>>> length 1497
>>>> R6#
>>>> *Jun  7 08:21:16.019: ISIS-Adj: Rec L2 IIH from 000c.293b.1023
>>>> (FastEthernet0/0.620), cir type L2, cir id 0000.0000.0020.01, length 1497
>>>> R6#
>>>> 
>>>> 
>>>> on XR
>>>> 
>>>> RP/0/0/CPU0:XR2#
>>>> RP/0/0/CPU0:XR2#show runn router isis
>>>> Sat Jun  7 08:22:26.395 UTC
>>>> router isis 1
>>>> is-type level-2-only
>>>> net 49.0001.0000.0000.0020.00
>>>> interface Loopback0
>>>>  passive
>>>>  address-family ipv4 unicast
>>>>  !
>>>> !
>>>> interface GigabitEthernet0/0/0/0.620
>>>>  circuit-type level-2-only
>>>>  address-family ipv4 unicast
>>>>  !
>>>> !
>>>> !
>>>> 
>>>> RP/0/0/CPU0:XR2#show runn int gig0/0/0/0.620
>>>> Sat Jun  7 08:22:38.025 UTC
>>>> interface GigabitEthernet0/0/0/0.620
>>>> ipv4 address 20.6.20.20 255.255.255.0
>>>> encapsulation dot1q 620
>>>> !
>>>> 
>>>> 
>>>> RP/0/0/CPU0:XR2#
>>>> RP/0/0/CPU0:XR2#show isis int gig0/0/0/0.620
>>>> Sat Jun  7 08:22:52.124 UTC
>>>> 
>>>> GigabitEthernet0/0/0/0.620  Enabled
>>>>  Adjacency Formation:      Enabled
>>>>  Prefix Advertisement:     Enabled
>>>>  IPv4 BFD:                 Disabled
>>>>  IPv6 BFD:                 Disabled
>>>>  BFD Min Interval:         150
>>>>  BFD Multiplier:           3
>>>> 
>>>>  Circuit Type:             level-2-only
>>>>  Media Type:               LAN
>>>>  Circuit Number:           1
>>>> 
>>>>  Level-2
>>>>    Adjacency Count:        0
>>>>    LAN ID:                 XR2.01
>>>>    Priority (Local/DIS):   64/none (no DIS elected)
>>>>    Next LAN IIH in:        6 s
>>>>    LSP Pacing Interval:    33 ms
>>>>    PSNP Entry Queue Size:  0
>>>> 
>>>>  CLNS I/O
>>>>    Protocol State:         Up
>>>>    MTU:                    1497
>>>>    SNPA:                   000c.293b.1023
>>>>    Layer-2 MCast Groups Membership:
>>>>      All Level-2 ISs:      Yes
>>>> 
>>>>  IPv4 Unicast Topology:    Enabled
>>>>    Adjacency Formation:    Running
>>>>    Prefix Advertisement:   Running
>>>>    Metric (L1/L2):         0/10
>>>>    Weight (L1/L2):         0/0
>>>>    MPLS LDP Sync (L1/L2):  Disabled/Disabled
>>>> 
>>>>  IPv4 Address Family:      Enabled
>>>>    Protocol State:         Up
>>>>    Forwarding Address(es): 20.6.20.20
>>>>    Global Prefix(es):      20.6.20.0/24
>>>> 
>>>>  LSP transmit timer expires in 0 ms
>>>>  LSP transmission is idle
>>>>  Can send up to 10 back-to-back LSPs in the next 0 ms
>>>> 
>>>> 
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>>>> 
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