Allowing multiple Vlans on access port

[msgforsunil]

Hello Team,

I have the following configurations in cisco CISCO7606 (R7000).

Can you please explain, if its meaningful to have the below configuration, wherein , we are allowing multiple vlans on the access port?  If no, then why do we allow such configuration?

interface FastEthernet4/45

switchport

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 124-127,423,478,493,578,699,751,787,895,987,1981

switchport mode access

end

interface FastEthernet4/46
switchport
switchport trunk allowed vlan 124-127,423,478,493,578,699,751,787,895,987,1981
switchport mode access
end

Thanks

Sunil Kumar

[Edison Ortiz]

The mode is set to access so the trunk configuration is ignored.

At this moment, that port is assigned to Vlan 1.

Can you post the output from 'show vlan' command?

[msgforsunil]

Please find the output below.  Listing only those ones that has "/" in it.  Please let me know, if you want complete output(which runs to multiple pages)

7606-001#show vlan | include /

1    default                          active    Gi2/6, Gi2/11, Gi2/12, Fa4/13, Fa4/15, Fa4/26, Fa4/27, Fa4/28, Fa4/34

                                                Fa4/38, Fa4/43, Fa4/45, Fa4/46, Fa4/47

205  VLAN0205                         act/unsup

211  VLAN0211                         active    Fa4/10, Fa4/17

369  VLAN0369                         active    Fa4/25

404  VLAN0404                         active    Fa4/48

712  VLAN0712                         active    Fa4/24

932  VLAN0932                         active    Gi2/5

1002 fddi-default                     act/unsup

1003 token-ring-default               act/unsup

1004 fddinet-default                  act/unsup

1005 trnet-default                    act/unsup

1182 VLAN1182                         active    Fa4/31

1190 VLAN1190                         active    Fa4/42

7606-001#

[Edison Ortiz · Accepted solution]

As I indicated, the port is set to access mode, not trunk:

1    default                          active    Gi2/6, Gi2/11, Gi2/12, Fa4/13, Fa4/15, Fa4/26, Fa4/27, Fa4/28, Fa4/34

                                                Fa4/38, Fa4/43, Fa4/45, Fa4/46, Fa4/47

When a port is set to trunk, it won't be listed in the show vlan command.

[msgforsunil]

May I know as why FastEthernet4/38 is listed above, when the configuration states, its trunk? Pasting the configurations below.

7606-001#show running-config interface FastEthernet4/38
Building configuration...

Current configuration : 163 bytes
!
interface FastEthernet4/38
switchport
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 699,712,751,787,987,3890
switchport mode trunk
end

Thanks

Sunil Kumar

[Edison Ortiz · Accepted solution]

Is the port up/up?

If the port is not connected, the trunk port reverts back to Vlan 1.

[msgforsunil]

Yes, the port is no up.

7606-001#show interfaces FastEthernet4/38

FastEthernet4/38 is down, line protocol is down (notconnect)

Thanks you Edison for your quick responses.

Thanks

Sunil Kumar

[msgforsunil]

And again, when the port is up, will the port be be back in trunk mode and how about the vlans configured on it?

Thanks

Sunil Kumar

[Edison Ortiz]

For port 4/38, yes - it will be in trunk mode.

Vlans 699,712,751,787,987,3890 will be allowed on this trunk.

You can verify if they are forwarding, with the show int trunk command.

[NSutfin]

No one really answered why you would want this...

But a couples of  reasons are that sometimes there are many services that converge over a singe port. In cellular you may have controller that connects to a switch and that controller may service circuit switched voice on a particular VLAN and LTE data on another VLAN but the baseband is controlled on a single unit,  Before you aggregate and send back over a common backhaul it is simpler from a design perspective set all ports as acces ports. As an additional security protocol and as a statistical gathering feature , many carriers do not allow untagged traffic to traverse the network.

[vipinsoni89]

I have two networks of those are using Private govt Network in Whole Campus by two separate Network providers.Both  of us using Vlan1. Some of our users needs both connectivity type but we are like to merge both networks are we already connected over L3 connectivity. So We need this solution for a standby Network solution for some users. Permitting for new vlan creation is not possible to us. So please help.

[Georg Pauwen]

Hello,

what exactly are you looking for ? Restricting access to users in the same VLAN (1) ?

[vipinsoni89]

As attached diagram Network A is responsible for IP Phone Communication and  B is used as ILL purpose whenever a user need both facilities we need to provide two separate cables to him on seat from both Network Racks. We would like to make it working via single wire but we have problem that both VLANs are used as default.