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Webcast-Catalyst9k
New Member

Two VLAN Interfaces on one AccessSwitch but witch Source IP Adr.?

Hi!

I configured a second VLAN Interface of my Access Switches. Since them VPMS doesn´t work anymore. I already know the reason but I doesn't know how to fix the Problem.

The Management VLAN is 191 and this is also the Native Vlan. But since I added the second VLAN Interface 76, the Switch take these IP Adr. as Source IP Adr. But the IP network VLAN 76 will not be routed in the network, for security reasons. How can I force the Switch that he will take the IP Adr. of interface VLAN 191 as source IP Adr? Does the Switch always take the lowest VLAN Interface Source IP Adr.?

!

interface Vlan1

no ip address

no ip route-cache

shutdown

!

interface Vlan76

ip address 192.168.71.145 255.255.255.0

!

interface Vlan191

ip address 172.24.191.145 255.255.255.0

no ip route-cache

!

ip default-gateway 172.24.191.254

6 REPLIES
Cisco Employee

Re: Two VLAN Interfaces on one AccessSwitch but witch Source IP

What kind of switch is this? If this ia an XL or 2950, you can have only one VLAN interface active. No value in having more than one VLAN interface as this is a L2 switch only and the L3 VLAN interface is used for management purpose only(ping/telnet etc).

New Member

Re: Two VLAN Interfaces on one AccessSwitch but witch Source IP

Hi!

It's am Cat3550 with SMI Image.

Cisco Employee

Re: Two VLAN Interfaces on one AccessSwitch but witch Source IP

Can you paste the output of sh ver and sh ip interface brief?

Bronze

Re: Two VLAN Interfaces on one AccessSwitch but witch Source IP

I would think that the decision of which source IP to use would depend on which VLAN the packet in question is destined to. For example, for packets originating from the switch destined to a device in VLAN191, it would use 172.24.191.1, and likewise for VLAN76. Is this not what you're experiencing?

New Member

Re: Two VLAN Interfaces on one AccessSwitch but witch Source IP

These access switch act as vmps client. And the client request to the vmps server doen't work because the switch take the "wrong" source ip adr.. If the switch take the source ip adr. of vlan 191, everything works fine.

Bronze

Re: Two VLAN Interfaces on one AccessSwitch but witch Source IP

What's the IP of the VMPS server? As far as I know, the source IP of a packet destined to the VMPS server should only be that of the VLAN 76 interface if such traffic is being routed out that interface. What is the output of 'show ip route x.x.x.x', where x.x.x.x is the VMPS server address? Some routing protocols will let you change the source IP of protocol packets to something other than the IP of the outbound interface, but I don't see a VMPS command to do this.

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