Re: [Isis-wg] [spring] Handling same SID mapped to different prefixes and vice versa cases

[Pushpasis Sarkar <[e-mail]>]

HI Peter,




On 10/9/15, 10:10 AM, "Peter Psenak" <[e-mail]> wrote:

>Hi Pushpasis,
>
>On 10/8/15 18:41 , Pushpasis Sarkar wrote:
>> Hi Peter,
>>
>>
>>
>>
>> On 10/8/15, 6:03 PM, "Peter Psenak" <[e-mail]> wrote:
>>
>>> how do you envision to find out the node originating a prefix in case of
>>> inter-area prefixe?
>> [Pushpasis] The ABR on the originating area/level should be able to detect the anomaly like other nodes in the same area/level and block re-advertisement.
>
>Node N1 in area 1 advertises prefix P1 with SID X. ABR1 advertises P1 to 
>area 0.
>Node N2 in area 2 advertises prefix P2 with SID X, ABR2 advertises P2 to 
>area 0.
>
>Node 3 in area 0 get these two prefixes P1 and P2 from two different 
>ABRs. How does it know that the originators for P1 and P2 are different? 
>Do you expect the ABR1 and ABR2 to detect the collision and withdraw SID 
>advertisement to area 0? If yes, that may become source of all sorts of 
>problems.
[Pushpasis] Nodes in area 0 can see that for the same prefix there are two prefix-sid advertisements from ABR1 and ABR2 but another advertisement (not re-advertisement) from Node 3. They should then not program a IP->MPLS or MPLS->MPLS route in the FIB and raise a syslog. I am not proposing a withdraw of the prefix-sid subtlv. The syslog should notify the operator of the misconfiguration scenario.

Thanks
-Pushpasis
>
>thanks,
>Peter
>
>>
>> Thanks
>> -Pushpasis
>>
>