[j-nsp] ISIS general questions

[Net MailingList]

Hi,


I would like to ask some generic questions about ISIS configuration.

1. Is ISIS authentication part of good current practices in large backbone?

2. In the case of an Ethernet and STM backbone, that already has Frame Check Sequence functionality, is it still necessary to enable checksum for IS-IS packet? Is this option used only in case the L2 protocol does not provide any FCS?

3. Let's imagine a network of 30 routers, 100 IS-IS routes within 20 PoPs.
Only the loopbacks, point-to-point links and backbone LAN will be advertised within ISIS.
All the rest (Internet routes, Data centers'LAN, customers' pool of addresses, customers LAN and connections from PE to CE) will be advertised by iBGP with route-reflectors.
My intention is to have a big flat network, within a single area where all the IS-IS enable interfaces will be Level2 only.
Whould you see any practical issue in this design?


4. About LDP/ISIS synchronisation:

Scenario1: we don't configure "ldp-synchronization {enable;}", my understanding is that:
- 1. ISIS converges
- 2. Some IP traffic can routed on the backbone (excluding MPLS VPN and Internet routes for example)
- 3. LDP converges, LSP are established
- 4. All Taffic is tagged switched

Scenario2: we do configure "ldp-synchronization {enable;}", my understanding is that:
- 1. ISIS converges
- 2. No IP Traffic can be routed on the backbone as the links are advertised with the maximum metric
- 3. LDP converges, LSP are established
- 4. All Taffic is tagged switched

Are those scenarii correct?


5. Concerning BFD (bidirectional forwarding detection), when Hellos are not received anymore, is the interface status declared down? Or is it only the ISIS adjacency that is torne down? What if the Hellos are blocked only in one direction?

6. Given that our backbone is build over Metro-Ethernet and STM, can I safely assume that the MTU can only be is symetrical? If not (why?) it becomes necessary to configure some padding (strict maybe)

Thank you very much in advance for your time.

Christophe