[c-nsp] 6500 Series ifindex

[Christophe Fillot]

Michael Balasko wrote:

>Does anyone know of a way to access the "file" that the switch uses to
>track ifindex's in NVRAM? 
>The jist of the issue is we are doing a Sup2 to 720 upgrade and we would
>like to preserve the ifindex numbers. Cisco says it can't be done, and
>I'm thinking that's not entirely true. Can anyone help? 
>
Hello,

I took a look on an ifIndex-table generated by a c7200 router. The
output of "sh snmp mib ifmib ifIndex" gives:

I0#sh snmp mib ifmib ifindex
ATM1/0: Ifindex = 11
ATM1/0-aal5 layer: Ifindex = 14
ATM1/0-atm layer: Ifindex = 12
ATM1/0.0-aal5 layer: Ifindex = 15
ATM1/0.0-atm subif: Ifindex = 13
ATM1/0.1-aal5 layer: Ifindex = 18
ATM1/0.1-atm subif: Ifindex = 17
FastEthernet0/0: Ifindex = 10
Null0: Ifindex = 16
POS3/0: Ifindex = 9
Serial2/0: Ifindex = 1
Serial2/1: Ifindex = 2
Serial2/2: Ifindex = 3
Serial2/3: Ifindex = 4
Serial2/4: Ifindex = 5
Serial2/5: Ifindex = 6
Serial2/6: Ifindex = 7
Serial2/7: Ifindex = 8

A partial hexadecimal dump of the file (copied to a Unix machine) gives:
0000: 00 00 00 12 00 00 00 0b 00 00 00 03 41 54 4d 31 ............ATM1
0010: 2f 30 00 00 00 00 00 00 00 1d 00 00 00 0e 00 00 .0..............
0020: 00 03 41 54 4d 31 2f 30 2d 61 61 6c 35 20 6c 61 ..ATM1.0.aal5.la
0030: 79 65 72 00 00 00 00 00 00 00 1c 00 00 00 0c 00 yer.............
0040: 00 00 03 41 54 4d 31 2f 30 2d 61 74 6d 20 6c 61 ...ATM1.0.atm.la
0050: 79 65 72 00 00 00 00 00 00 00 1f 00 00 00 0f 00 yer.............
0060: 00 00 03 41 54 4d 31 2f 30 2e 30 2d 61 61 6c 35 ...ATM1.0.0.aal5
0070: 20 6c 61 79 65 72 00 00 00 00 00 00 00 1e 00 00 .layer..........

I guess that the file consists in consecutive interface records, each
interface record being defined as follows:

 rec_len       (4 bytes) : length of the record, minus 4
 if_index      (4 bytes) : ifIndex value
 unknown_value (4 bytes) : unknown / always 0x00000003 ?
 if_name       (N bytes) : interface name

So, I suggest that you copy your current ifIndex-table file and check if
its format is the same. In my opinion, you can simply take the
ifIndex-table file and copy it to your new Sup720. I've checked with one
of my 7600 (Sup720 too), this is identical.

Hope this helps.

Chris.