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Webcast-Catalyst9k
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Newb question 3750 - trunking

Hi,

first...not network expert know basics but been tasked with sorting this so go easy on me

got 3 x 3750E series switches, spread across two rooms. switches are basically default config right now...reset today from scratch.

Room1 -

cisco01 / 172.16.102.241 (vlan 1) - twingig FC module FC patch 18 plugged into Gi1/0/26

cisco02 / 172.16.102.242 (vlan 1) - twingig FC module FC patch 21 plugged into Gi1/0/50

Room 2 -

cisco04 / 172.16.102.244 (vlan 1) - twingig FC module FC patch 18 plugged into Gi2/0/49

                                                                                       FC patch 21 plugged into Gi2/0/50

I guess in terms of connections this looks like this

cisco01-Gi1/0/26->----------FC--------<Gi2/0/50-cisco04-Gi2/0/49>--------FC--------<Gi/1/0/50-cisco02>

At this time there are NO other connections into any of these switches.

Noticed that on cisco01 console it has the following repeating error:

"IP-4-DUPADDR duplicate address 172.16.102.241 on vlan 1 sourced by xxxx:xxxx:xxxx"

and also on cisco02 console it has the following same/similar repeating error:

"IP-4-DUPADDR  duplicate address 172.16.102.242 on vlan 1 sourced by xxxx:xxxx:xxxx"

I cannot recall the MAC addresses exactly but if I search for the MAC address mentioned in the above two errors by running:

show mac-address-table | inc xxxx

then on both cisco01 and cisco02 the MAC returned is that of the port the FC cable is patched into on that switch, so Gi1/0/26 for cisco01 and Gi1/0/50 for cisco02

on all 3 switches the above port setup is basically:

interface GigabitEthernetX/0/XX
switchport trunk encapsulation isl
switchport mode trunk

given that this all seems to tie in to the FC links between the switches it seems like i've made some basic error in the configuration of these ports that the FC cables are patched to.

anyone spot what is wrong and why the two switches at either of the chain as it were seem to see their own vlan 1 addresses as duplicates???

thanks in advance!!!

1 REPLY
Hall of Fame Super Blue

Re: Newb question 3750 - trunking

Can you post full config for the switches ?

Jon

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