IS-IS configuration - help required

simonixus · ‎05-01-2013

Thanks in advance for your support

I have this question below:

I have 2 routers C1 and C2 connected to NMS in Area 1, the NMS is configured with ISIS Level-1

These 2 routers are connected to 2 other routers A15 and A17 with Serial links

A15 is in Area 15 and configured with ISIS type Level-1 on the E0, and Level-2 on the serial link

A17 is in Area 17 and configured with ISIS type Level-1 on the E0, and Level-2 on the serial link

No links between Area 15 and Area 17

What is the optimal configuration for the E0 and S0of C1 and C2

Should they be L1L2 or L2 on the serial link and L1 on the Ethernet ?

A drawing is attached for your quick reference

Thanks again for the support

Simonixus

O Bitar · ‎05-01-2013

Hi Simon,

You need to configure L1/L2 ISIS router on the routers that are going to inject a default routes to L1 areas. And judging from your drawing the placment of the L1/L2 router can either be on the As routers or the Cs router depending on the hardware. If you configure both A routers as L1/L2 then it is best to configure bot C routers as L2 only to minimise the memory used.

Omar

simonixus · ‎05-01-2013

hello and thanks for the reply

do you consider a router with Ethernet configured as L1 and Serial configured as L2 an L1/L2 router ?

thanks

O Bitar · ‎05-01-2013

Hi Simon,

I thought you are applying the router type under the ISIS process and left all interface to the default, the main point to consider when selecting L1/L2 routes is ,which router will host both database, have enough memory and to ensure that L2 area is contiguous.

Omar

simonixus · ‎05-01-2013

thanks again

normally there is no connection between area 15 and area 17 , only area 1 will communicate with area 15 and area 17

and vice versa, area 15 will communicate with area 1 and area 17 will communicate with area 1

the routers C1 and C2 are the big routers A15 and A17 small routers

if I am configuring the interfaces individually on C1 and C2, shall I put the Ethernet as L1 and the serial as L2, as they are on the routers A15 and A17 ?

thanks again for your time and effort to help