02-26-2010 01:23 PM - edited 03-06-2019 09:55 AM
Hello, I have not been able to connected my 3750 to my 2821 through the Gi0/1 fixed interface on the 2821. The 2821 has 1 serial interface, 2 fixed Gigabit Ethernet Interfaces and a card with 9 Fastethernet interfaces. The serial is used to connect to my WAN. I can connected the 3750 to any one of the ports of the 9 FastEthernet card when i configure it as a trunk. I set up the Gi0/1 port on the 2821 the same way, the router doesn't see the switch. I can get the router's mac-address from the switch however. The 2821 has VLANs on it. The 3750 has similar VLANs on it. How do i configure the Gi0/1 for it to see the switch?
here is the current config for desired port:
(2821)
interface GigabitEthernet0/1
no ip address
no ip redirects
no ip unreachables
no ip proxy-arp
ip route-cache flow
duplex auto
speed auto
no mop enabled
Here is the config for the working port
(2821)
interface FastEthernet0/1/3
switchport mode trunk
switchport voice vlan 6
spanning-tree portfast
I did try putting switchport mode trunk on int Gi0/1 but had no joy doing that.
I tried to give that port an ip address but would get overlap errors with VLAN1.
02-26-2010 01:49 PM
Hi,
Gi0/1 is routed port and not a switch port. If you want trunk it with multiple vlans, you need to create a sub-interface for each vlan.
for example
int gi0/1.1
int gi0/1.2
and so on.
Then add the IP address to the sub-interface and use encapsulation dot1Q and the vlan id
HTH
Reza
02-27-2010 06:26 AM
Hello,
I did create the sub-interface. I wasn't able to assign an IP address to it.
2821-1#config t
Enter configuration commands, one per line. End with CNTL/Z.
2821-1(config)#int gi0/1.1
2821-1(config-subif)#ip address 10.x.x.6 255.255.255.0
% Configuring IP routing on a LAN subinterface is only allowed if that
subinterface is already configured as part of an IEEE 802.10, IEEE 802.1Q,
or ISL vLAN.
02-27-2010 06:41 AM
Hi,
You need to add 802.1q trunk before you can assign your IP
HTH
Reza
03-01-2010 05:12 PM
Thanks everyone for your assistance
Still no joy. Not able to add an IP address on to the interface. I want the VLAN1 traffic to pass back and forth through this interface and to the connected switch.
2821-1#sho run int gi0/1.1
Building configuration...
Current configuration : 109 bytes
!
interface GigabitEthernet0/1.1
encapsulation dot1Q 1 native
no snmp trap link-status
no cdp enable
end
2821-1#config t
Enter configuration commands, one per line. End with CNTL/Z.
DET-MDF-2821-1(config)#int gi0/1.1
DET-MDF-2821-1(config-subif)#ip address 10.x.x.6 255.255.255.0
% 10.7.0.0 overlaps with Vlan1
02-26-2010 02:22 PM
G0/1 and G0/2 is a routed port so you need to configure "router-on-a-stick" but your 6-port card is a chop-down version of a 2950 or a 3750, so it's a switch.
Configuring InterVLAN Routing and ISL/802.1Q Trunking on a Catalyst 2900XL/3500XL/2950 Switch Using an External Router
http://www.cisco.com/en/US/tech/tk389/tk815/technologies_configuration_example09186a00800949fd.shtml
02-27-2010 04:10 AM
did you get the error "Command rejected: [interface] not a switching port" when you applied the trunk config to gi0/1? To change a L3 interface to a L2 switching port, use the command switchport e.g.
interface GigabitEthernet0/1
switchport
switchport mode trunk
hth
02-27-2010 06:28 AM
Hello,
No I did not get that error when I applied the switchport mode trunk.
03-01-2010 05:26 PM
More Information:
Vlan Config on 2821
interface Vlan1
ip address 10.x.x.1 255.255.255.0
no ip redirects
no ip unreachables
no ip proxy-arp
ip route-cache flow
no autostate
Port config on 3750
interface GigabitEthernet1/0/47
switchport trunk encapsulation dot1q
switchport mode trunk
switchport nonegotiate
!
interface Vlan1
ip address 10.x.x.5 255.255.255.0
ip helper-address 10.x.x.24
03-01-2010 06:45 PM
Hi,
As per your configuration which you have pasted here, already you have configured vlan 1 as L3 vlan with ip segment 10.x.x.0/24 and the same segment of ip range you trying to assign into fast ethernet sub-interface.
So, As you know,It is not possible to assign same segment of IP range into two different L3 interfaces.
your configuration in the router should be like this
no int vlan 1
int gi0/0
no ip address
int gi0/0.1
encapsulation dot1q 1 native
ip address 10.x.x.1 255.255.255.0 // As per your network range //
Finally you need to remove the ip address in vlan 1. You cannot make the router as switch 100 %. But we can configure router-on-stick method to simulate switch functinality to router.
For more information have a look into this URL, which will clarify more.
http://www.cisco.com/en/US/tech/tk389/tk815/technologies_configuration_example09186a00800949fd.shtml
regards
Karuppu
03-02-2010 04:28 AM
Hello,
We were using the 2821 with the 9 port ethernet switch card as the branch office router and switch. We had a need for more ports and aquired a 3750. On the 2821 we have multiple VLANS set up. Throughout our domain, the switches all have the same VLANS configured. When I get this first one configured I will be creating more interfaces and putting VLANS on those interfaces.
To clarify I need to remove the VLAN1 from the L3. Do I assign the current IP address of the router to the Gi0/1.1 interface or a different one? Because the rest of the network is looking for that router (and LAN segment) at the 10.x.x.1 address.
A question I have here would be would the Gi0/1.1 have the full gigabit bandwidth or will it be reduced by the number of subinterfaces I configure?
Thanks.
03-02-2010 04:35 AM
Hi,
Do I assign the current IP address of the router to the Gi0/1.1 interface or a different one? -- Yes. you can assign the vlan 1 ip address into gi0/1.1
And if you want to permit more vlan over this physical interface, create the required number of interfaces and assign those sub-interfaces into the respective vlan.
A question I have here would be would the Gi0/1.1 have the full gigabit bandwidth or will it be reduced by the number of subinterfaces I configure?
Even if you are creating the 10 sub-interfaces in a single gi0/1, the maximum throughput will be 1Gbps. it will be shared into the multiple sub-interfaces.
Hope this clarified to your question. If you need more info, raise your questions.
regards
karuppu
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