Cisco 2921 with EtherSwitch

[shaucall46]

   Scratching my head with this one, configuring up a 2921 router for remote site which is fitted with 24 port Etherswitch module.

As part of this setup I have defined 3 vlans on the router, but when I go onto etherswitch and for example set switchport access to access vlan 3 it is not aware of this vlan.

Do I have to set up trunk inbetween Router and its etherswitch?

Wish I had ordered seperate switch as it would have been easier or am I missing something.

sho vlan-switch shows my vlans but on swicth sho vlan brief does not.

Any help appreciated.

[Reza Sharifi]

Yes, you need to set up trunk between the switch module and the router.  If I remember correctly, it is gi0/1, but not sure.  It is basically the interface that connect the switch to the router (internally)

HTH

[darren.g · Accepted solution]

shaucall46 wrote:
   Scratching my head with this one, configuring up a 2921 router for remote site which is fitted with 24 port Etherswitch module.
As part of this setup I have defined 3 vlans on the router, but when I go onto etherswitch and for example set switchport access to access vlan 3 it is not aware of this vlan.
Do I have to set up trunk inbetween Router and its etherswitch?
Wish I had ordered seperate switch as it would have been easier or am I missing something.
sho vlan-switch shows my vlans but on swicth sho vlan brief does not.
Any help appreciated.

Yeah, as Reza said, you need to configure a trunk on the backplane to "link" the switch module and the router.

You also need to manually create the VLAN's in the switch module as well as the router module.

This is an example from my config from a 2921 with an SM-ES3-24-P switch module in it.

Router#show run

interface GigabitEthernet1/0

ip address 1.1.1.1 255.255.255.0

!

interface GigabitEthernet1/0.3

encapsulation dot1Q 3

ip address 10.10.12.254 255.255.255.0

ip helper-address 10.10.12.2

switch#show run

vlan 3

name lan

interface GigabitEthernet0/26

switchport trunk encapsulation dot1q

switchport mode trunk

interface Vlan3

ip address 10.50.12.250 255.255.255.0

ip helper-address 10.50.12.2

switch#show vlan brief

VLAN Name                             Status    Ports

---- -------------------------------- --------- -------------------------------

1    default                        active    gi0/25

3    lan                             active    Fa0/2, Fa0/3, Fa0/4, Fa0/5, Fa0/6, Fa0/7, Fa0/8, Fa0/9, Fa0/10,

                                                   Fa0/11, Fa0/12, Fa0/13, Fa0/14, Fa0/15, Fa06, Fa0/17, Fa0/18,

                                                   Fa0/19, Fa0/20, Fa0/21, Fa0/22, Fa0/23, Fa0/24

G1/0 (router side) and G0/26 (switch side) are 'internal' ports which link via the backplane and connect the two devices together. The 1.1.1.1 address in the router is simply a placemarker and not used (I didn't set this up - I would have used an "ip unnumbered" most likely) in the routing setup.

Note the "encapsulation dot1q 3" line on the sub-interface on the router. This is what creates the trunk which links to the switch module, and allows routing to happen between the switch module and the router ports.

Cheers.

[shaucall46]

Thanks Guys much appreciated.

I was just about there I had set up the trunk on router but on the Etherswitch I saw there was 2 ports UP/UP Gig0/25 and Gig 0/26 so was unsure which one was backplane link, if its Gig 0/26 what is 0/25 ?

Another unusual thing is all the documnetation and as you have pointed out the router port to etherswitch is Gig1/0 but this one is Gig1/1, I cannot connect to it as per documentation service-module interface session, this command will not recognise the interface, also wont let me apply an IP to that interfcae.

To connect to switch( I am remotely consolde into router via a Perle Iolan DS1 terminal server - great device) I have to telnet to switch by telnet x.x.x.x (loopback addrss of router) 4067 (which is line associated with etherswitch), this method works but it isnt very good.

Is it possible etherswitch is fitted in wrong slot, I would have thought it would have worked in any suitable slot.

Thanks

[shaucall46]

Ok Guys got it cracked now.

Etherswitch was on Gig 1/0 but someone had shut the port and put description on port G1/1 saye it was connection to Etherswitch grrrr.

Config all done now and faith restored in EtherSwitch modules, now behaving as if it is a seperate switch.

Thanks

again

[darren.g]

shaucall46 wrote:
 Thanks Guys much appreciated.
I was just about there I had set up the trunk on router but on the Etherswitch I saw there was 2 ports UP/UP Gig0/25 and Gig 0/26 so was unsure which one was backplane link, if its Gig 0/26 what is 0/25 ?
Another unusual thing is all the documnetation and as you have pointed out the router port to etherswitch is Gig1/0 but this one is Gig1/1, I cannot connect to it as per documentation service-module interface session, this command will not recognise the interface, also wont let me apply an IP to that interfcae.
To connect to switch( I am remotely consolde into router via a Perle Iolan DS1 terminal server - great device) I have to telnet to switch by telnet x.x.x.x (loopback addrss of router) 4067 (which is line associated with etherswitch), this method works but it isnt very good.
Is it possible etherswitch is fitted in wrong slot, I would have thought it would have worked in any suitable slot.
Thanks

G0/25 & G0/26 are *both* backplane connection ports.

On the router side, G1/0 & G1/1 match to them - G1/0 on the router side connects to G0/25 on the switch module, and the routers G1/1 connects to G0/26 on th switch module.

Cheers.

[richard@ifiresolutions.com]

Hi Darren,

I do not see this in my router as you describe. If I telnet to my etherswitch module 10.10.17.1 vlan 17 from my PC connected to a port in the etherswitch module, ip address 10.10.16.1 255.255.255.0 vlan 16 then the connection should go via the router since my pc is in a different VLAN to the address I am telneting to.

However, whilst in the telnet session, if I shutdown interface gig0/25 then my telnet session immediately terminates and the session hangs. If I do the same thing but shutdown Gig0/26 instead of Gig0/25 then the telnet session does not terminate and everything carries on as normal. This implies to me that Gig0/25 is actually the trunk port connecting through to the routers Gig1/1 MGF trunk port, rather than Gig0/26 as you describe.

The strange thing is that I was expecting that if I shutdown Gig0/26 then since this (by implication from above) would seem to be the other side of the Gig1/0 at the router, I was expecting the SERVICE-MODULE Gig1/0 SESSION command to fail to connect. But, this did not happen and I was still able to do everything when Gig0/26 was disabled. Although, when I disabled Gig0/26 a warning popped up relating to PoE and power loss to connected phones.

So, based on my testing Gig0/25 seems to be the trunk port connecting to the routers Gig1/1 interface, and Gig0/26 seems to be some unkown port relating to PoE but I haven't worked out what it does yet! There doesn't seem to be a corresponding etherswitch interface for the router Gig1/0 as this connects directly into the PCIe interface internally?

Do you agree, or do you see different behaviour?

If you agree, then it's etherswitch port Gig0/25 that needs to be configured as trunk to communcate with the router. If anyone does know what Gig0/26 is for then please let us know!

Richard.

[darren.g]

Richard Merrett wrote:
 Hi Darren,
I do not see this in my router as you describe. If I telnet to my etherswitch module 10.10.17.1 vlan 17 from my PC connected to a port in the etherswitch module, ip address 10.10.16.1 255.255.255.0 vlan 16 then the connection should go via the router since my pc is in a different VLAN to the address I am telneting to.
However, whilst in the telnet session, if I shutdown interface gig0/25 then my telnet session immediately terminates and the session hangs. If I do the same thing but shutdown Gig0/26 instead of Gig0/25 then the telnet session does not terminate and everything carries on as normal. This implies to me that Gig0/25 is actually the trunk port connecting through to the routers Gig1/1 MGF trunk port, rather than Gig0/26 as you describe.
The strange thing is that I was expecting that if I shutdown Gig0/26 then since this (by implication from above) would seem to be the other side of the Gig1/0 at the router, I was expecting the SERVICE-MODULE Gig1/0 SESSION command to fail to connect. But, this did not happen and I was still able to do everything when Gig0/26 was disabled. Although, when I disabled Gig0/26 a warning popped up relating to PoE and power loss to connected phones.
So, based on my testing Gig0/25 seems to be the trunk port connecting to the routers Gig1/1 interface, and Gig0/26 seems to be some unkown port relating to PoE but I haven't worked out what it does yet! There doesn't seem to be a corresponding etherswitch interface for the router Gig1/0 as this connects directly into the PCIe interface internally?
Do you agree, or do you see different behaviour?
If you agree, then it's etherswitch port Gig0/25 that needs to be configured as trunk to communcate with the router. If anyone does know what Gig0/26 is for then please let us know!
Richard.

Just because they're both present doesn't mean they're both configured to carry traffic between the router and the switch module.

From my 2911 with an SM module in it

R2#sh int sum

*: interface is up

IHQ: pkts in input hold queue     IQD: pkts dropped from input queue

OHQ: pkts in output hold queue    OQD: pkts dropped from output queue

RXBS: rx rate (bits/sec)          RXPS: rx rate (pkts/sec)

TXBS: tx rate (bits/sec)          TXPS: tx rate (pkts/sec)

TRTL: throttle count

  Interface                   IHQ       IQD       OHQ       OQD      RXBS      RXPS      TXBS      TXPS      TRTL

-----------------------------------------------------------------------------------------------------------------

  Em0/0                         0         0         0         0         0         0         0         0         0

  GigabitEthernet0/0            0         0         0        47         0         0         0         0         0

  GigabitEthernet0/1            0         0         0         0         0         0         0         0         0

  GigabitEthernet0/2            0         0         0         0         0         0         0         0         0

* GigabitEthernet0/0/0          0         0         0         0     10000        18      6000         7         0

* GigabitEthernet0/0/1          0         0         0         0   2128000       281    208000       186         0

* GigabitEthernet0/0/2          0         0         0         0    198000       181   2115000       280         0

  GigabitEthernet0/0/3          0         0         0         0         0         0         0         0         0

* GigabitEthernet1/0            0         8         0         0     15000        24         0         0         8

* GigabitEthernet1/0.3          -         -         -         -         -         -         -         -         -

* GigabitEthernet1/1            0         0         0         0         0         0         0         0         0

* Loopback0                     0         0         0         0         0         0         0         0         0

* Vlan1                         0         0         0         0         0         0         0         0         0

NOTE:No separate counters are maintained for subinterfaces

     Hence Details of subinterface are not shown

So I have G1/0 configured and carrying traffic

SW2#sh int sum

*: interface is up

IHQ: pkts in input hold queue     IQD: pkts dropped from input queue

OHQ: pkts in output hold queue    OQD: pkts dropped from output queue

RXBS: rx rate (bits/sec)          RXPS: rx rate (pkts/sec)

TXBS: tx rate (bits/sec)          TXPS: tx rate (pkts/sec)

TRTL: throttle count

  Interface               IHQ   IQD  OHQ   OQD  RXBS RXPS  TXBS TXPS TRTL

-------------------------------------------------------------------------

  Vlan1                    0     0    0     0     0    0     0    0    0

* Vlan3                    0     0    0     0  4000    4     0    0    0

  FastEthernet0/2          0     0    0 17728     0    0     0    0    0

  FastEthernet0/3          0     0    0 613327     0    0     0    0    0

  FastEthernet0/4          0     0    0     0     0    0     0    0    0

  FastEthernet0/5          0     0    0     0     0    0     0    0    0

* FastEthernet0/6          0     0    0  8537     0    0  9000    8    0

  FastEthernet0/7          0     0    0     0     0    0     0    0    0

* FastEthernet0/8          0     0    0  5036     0    0  9000    8    0

  FastEthernet0/9          0     0    0   425     0    0     0    0    0

  FastEthernet0/10         0     0    0     0     0    0     0    0    0

  FastEthernet0/11         0     0    0 4825764     0    0     0    0    0

  FastEthernet0/12         0     0    0    64     0    0     0    0    0

  FastEthernet0/13         0     0    0 765088     0    0     0    0    0

* FastEthernet0/14         0     0    0     0     0    0  9000    8    0

* FastEthernet0/15         0     0    0 617033     0    0  9000    8    0

* FastEthernet0/16         0     0    0     0     0    0  9000    8    0

* FastEthernet0/17         0     0    0     0     0    0  9000    8    0

  FastEthernet0/18         0     0    0     0     0    0     0    0    0

* FastEthernet0/19         0     0    0   193     0    0  9000    8    0

  FastEthernet0/20         0     0    0 618099     0    0     0    0    0

* FastEthernet0/21         0     0    0 617015     0    0  9000    8    0

* FastEthernet0/22         0     0    0     0     0    0  9000    8    0

* FastEthernet0/23         0     0    0     0     0    0     0    0    0

* FastEthernet0/24         0     0    0     0     0    0  9000    8    0

* GigabitEthernet0/1       0     0    0     0  9000    8 12000   19    0

* GigabitEthernet0/25      0     0    0     0     0    0     0    0    0

* GigabitEthernet0/26      0     0    0     0  1000    1 21000   28    0

And on the switch module, G0/26 receives this traffic

The other two ports are there, but are not configured - maybe they both *can't* be configured at the same time, but since I'm pulling this from a production router I'm not about to fiddle with it. Or maybe there's some deep Cisco logic I don;t understand, but for my configuration

G1/0 on the router module connects to G0/26 on the switch module

I don't know why yours behaves differently.

Cheers.

[richard@ifiresolutions.com]

Hi Darren,

I think you agree with me in that case? In your original post you had said that Gig1/0 on the router connected to Gig0/25 and Gig1/1 on the router connected to Gig0/26. I was querying this, and your latest post with "sh int sum" seems to confirm this as your Gig1/0 port is connecting through to Gig0/26, not Gig0/25?

I guess it depends on what the traffic is that is flowing through your Live router, but since it is entering your Gig1/0 port on the router side, it seems this is not MGF traffic as that would use Gig1/1?

The one thing I am not clear on is around traffic flowing from an MGF module to the router. All of the logical Cisco block diagrams show the MGF connected to the CPU, which implies to me that router traffic from the WAN going to a device conneced to the switch module would go via the router CPU straight into the MGF (Gig1/1) and then arrive on the switch module MGF interface to be forwarded on. I'm not sure if this is really the case or not, as it may be that router CPU packets do not go via MGF at all, which is why they seem to go through your Gig1/0 and Gig0/26 interfaces?

The weird thing is that even with BOTH Gig0/25 and Gig0/26 set to "shutdown" on the switch module, I can still connect to the switch using "service-module gig1/0 session" from the router. I can't explain this properly at the moment unless this method does not use either of these ports?

[darren.g]

Richard Merrett wrote:
The weird thing is that even with BOTH Gig0/25 and Gig0/26 set to "shutdown" on the switch module, I can still connect to the switch using "service-module gig1/0 session" from the router. I can't explain this properly at the moment unless this method does not use either of these ports?

I believe that connection method uses a different path, not one of the backplane ports.

I have had a tough time wrapping my head around the 29xx architecture - I added a HWIC module to my routers, and as far as I could find otu out the only way to integrate it into the same switching fabric as the SM module was to physically cable them together - so anything I say about your comments above is pure conjecture in my part based on potentially inaccurate interpretations of Cisco's documentation. :-)

Cheers

[richard@ifiresolutions.com]

So, after a long drawn out TAC case with Cisco I think I finally have the answer confirmed by Cisco.

So they say Gig0/25 is the MGF connection, as you had identified earlier. This is apparently used for all traffic to/from the router and as the gateway to other router modules, even if those other modules don't suppot MGF. (I can't validate that bit as my modules are all MGF-enabled.)

Gig0/26 is the legacy connection to the router CPU, but not used in practical terms although it is used for initial configuration before the MGF i set up (i.e. when you first get the module). After MGF is set up, telnetting into the switch should use Gig0/25 via the MGF.

Using the "session" commad from the router causes a console session to be opened to the etherswitch, similar to plugging a console cable into the router. This command will always establish a connection even if Gig0/25 Gig0/26 are SHUT. This makes sense to me, as otherwise shutting down those ports would lock you out of the etherswitch.

So, in my setup Gig0/26 isn't used at all and all traffic flows through Gig0/25. I've had the router end of Gig0/26 SHUT for a while now (router int Gig1/0) and it hasn;t caused any issues that I can see. I also have that port in a seperate firewall zone, again with no issues so it does seem that Gig0/25 (router Gig1/1) is exclusively used via MGF.

I agree with what you said about non-MGF modules and having to cable the modules together to use the same switching fabric. Interestingly,Cisco have also confirmed that if you have two single-wide etherswitch modules installed in the same router, even though their documentation says that they will act like one device and not use router CPU, in reality they still communicate with either other via the MGF and therefore there is a 1Gbps bottleneck between devices on one SM to devices on the other SM. Lin-rate fabric switching is only achived within the same SM, do if you need 48 ports then the double-wide SM will give better performance than two single-wide SMs in the same chassis. AFAIK there is no way to cable those devices together directly.

Richard.

[alkhatimvip]

Can I balance traffic between router and switch
by allowing some VLANs to go via g0/25 (issue this command under interface mode switchport trunk allow vlan a,b,c) and other VLANs go via g0/26 (switchport trunk allow vlan x,y,z)?