TFTP and ISL Trunking

[StarTAC]

hi guys..

i have configured a router for ISL Trunking using ethernet sub-interfaces, and it works.. the problem is the router is low on flash, so i am booting the IOS image off a TFTP server..

i have configured PortFast on the switch so there's no STP convergence on it.. so the intefaces is up and running in under 1 second.. i can boot the image off the TFTP server..

however, when i enabled the ethernet sub-interfaces, i can't boot off the TFTP server anymore.. lucky for me i had a smaller IOS on the router flash, so i booted it and moved the main ip address from the sub-interface onto the major interface.. i can now boot off the TFTP server..

so my question is, is there a way i can maintain my ethernet sub-interfaces and continue to boot off the TFTP server, without assigning an ip address to the major ethernet interface..?..

all help appreciated..

 

[fmonteiro]

I am sorry but I was unable to really understand your problem. You configured the router for ISL Trunk using ethernet sub-interfaces, and it worked... However, when enabling the ethernet sub-interfaces you can't boot from the TFTP server. So, what really worked?

 

[StarTAC]

i booted the IOS off a TFTP server, enabled and configured ISL trunking on the ethernet sub-interfaces.. i disabled IP processing on the major ethernet sub-interface... all IP addresses were on the ethernet sub-interfaces...

when i rebooted, i couldn't access the TFTP server, so i couldn't load the IOS image.. i booted the old, on-flash IOS, enabled IP processing on the major ethernet interface and was able to boot the IOS off the TFTP server...

my question - is the ethernet sub-interface only enabled after the IOS is loaded..?.. can it be used to boot an IOS image off a TFTP server...?....

i hope it makes sense now..

all help appreciated..

 

[fmonteiro]

I got it know. The boot from the TFTP server works only when the IP address is assigned to the physical interface. It makes sense for me. The bootstrap is a very small subset of the IOS. I believe it is unaware on logical interfaces (I mean sub-interfaces). But, as I am not sure I would like to ask for a second opinion from anybody else in the forum.

 

[tschouten]

Fmonterio is right, the bootstrap is where your boot from tftp resides and this is completely unaware of logical (software/sub-interface) ports.

 

[tschouten]

What you could try to do for example is say ip address you want use the subinterface for is 192.10.3.1 255.255.0.0
So you put ip address of 192.10.4.1 255.255.0.0 on the main address and block it with an ACL for everything but the tftp. Not to mention you could make it a passive interface so no updates go in or out of it but the sub-interfaces work like they are designed.

 

[StarTAC]

cheers.. that's all i needed to confirm, that the sub-interface is only powered by the full IOS, and not by the bootstrap..

thanks all..