CCIE Pursuit Blog

January 6, 2008

Internetwork Expert Volume III: Lab 1 – Section 1

1 Troubleshooting

First error:

I initially missed this error on my fly-by at the beginning of the lab, but caught it later on.  It was an SVI that had been configured with an incorrect second octet:

sw2(config)#do sh run int vlan82
interface Vlan82
 ip address 192.1.1.8 255.255.255.0
end

sw2(config)#int vlan82
sw2(config-if)#ip add 192.10.1.8 255.255.255.0

Second error:

The second error was a little more complicated, but easier to spot as you won’t be able to build your Layer 3 Etherchannels until you fix it.

As you try to configure a Layer 3 Etherchannel with the IP address and mask listed on the topology, you’ll encounter the following error:

sw2(config-if)#ip add 140.1.0.8 255.255.255.128
Bad mask /25 for address 140.1.0.8

If you take a look at the final octet of the address and the mask, you’ll find that the address is in the zero (140.1.0.0) subnet:

Address  .8    0|0001000
Mask     .128  1|0000000

This should not be a problem as “ip subnet-zero” is enabled by default:

ip subnet-zero

But, IE turned it off in the initial configuration:

sw2(config-if)#do sh run | i subnet-zero
no ip subnet-zero

sw2(config-if)#ip subnet-zero
sw2(config)#int po23
sw2(config-if)#ip add 140.1.0.8 255.255.255.128

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1 Comment »

  1. […] Mind the order of operations for Layer 3 Etherchannels during this task.  The IE solution guide has a nice example of the correct order of operations.  Also, this task asks you to “use all remaining directly connected inter-switch links” between sw2 and sw3 as well as sw2 and sw4.  This gets a little difficult due to the initial configurations setting some of the connected ports in shutdown.  Unless you are given a layer 2 map with all of the inter-switch connections listed in the actual lab, this would be a pain in the ass as you would need to do a “no shut” ports on sw2, sw3, and sw4 to see the connections via “show cdp neighbor”.  Also note that both Layer 3 Etherchannels use a /25 (255.255.255.128) mask.  You’ll discover one of the two initial configuration errors during this task. […]

    Pingback by Internetwork Expert Volume III: Lab 1 - Section 2 « CCIE Pursuit — January 6, 2008 @ 10:14 pm | Reply


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