SM-1T3/E3 Service Module Configuratioin questions

[bberry]

Hello,

I am in the process of configured a new SM-1T3/E3 card in one of our 2911 routers to support a new T3 connection. THis is the first time I have ever configured one of these so am trying to understnad all the piece parts. I have gone through the configuration guide on CCO and working through the configuration sample from our ISP. The Cisco guide makes it look like I need to configure DHCP on the router as it says the cards gets an IP address from the platform at boot up. The ISP sample does not reference this anywhere in their manual. I went through the steps to configure the card type and controller and it did add serial as well as an SM interface into my configuration. There was an IP address automatically added to the SM interface. 

My question is this. Do I need the SM interface? The ISP sample uses the serial interface to create a multi-point interface. I pulled the IP address off the SM interface as the auto assigned one is active address space elsewhere on my network. If I do have to have the SM interface configured does it matter what IP address I give it?

Anyone have additional information, guides, videos, etc. that I can go through to better understand this?

Thanks in advance....

Brent

[Giuseppe Larosa]

Hello Brent,

may you provide the Cisco link you are following?

usually SM stands for service module and the SM interface in this cases is used to manage the service module and to access to its shell from the router.

So if this is a real service module the SM interface may be needed for management purposes so I would leave an IP address on it that is likely provided by the router on an internal link to the module.

However, I would not expect a service module for providing E3/T3 serial unless this module is capable of channelization that is to allocate multiple T1 inside the T3, in this case it becomes a sort of ADM and would explain why a service module is needed.

Edit:

I have found the following reference to a module named SM-X-e3/t3 service module

https://www.cisco.com/c/en/us/products/collateral/routers/4000-series-integrated-services-routers-isr/data_sheet_c78-728546.html

It has a built in DSU but it does not support channelization.

Edit2:

I can confirm the SM interface is for management and troubleshooting purposes

Q.    What is the interface name when the ISR G2 router boots up with the T3/E3 module in the running configuration?

A.     The module is listed as interface sm slot/(subslot+1). For example, if the T3/E3 module is present in slot 1, interface sm 2/1 is the configuration.

This connection is used to perform debugging and to set up a console connection to the module. It is not used for data traffic. This port is assigned an IP address from the Virtual Route Forwarding (VRF) Dynamic Host Configuration Protocol (DHCP) pool.

from this service module Q&A

https://www.cisco.com/c/en/us/products/collateral/routers/4000-series-integrated-services-routers-isr/qa_c67-728547.html

Hope to help

Giuseppe

[bberry]

This is the link for the configuration guide I am following ...

https://www.cisco.com/c/en/us/td/docs/routers/access/interfaces/sm/software/configuration/guide/configt3e3.html

Brent

[Giuseppe Larosa]

Hello Brent,

according to the configuration guide you have provided the communication of the service module with the backplane requires the interface sm <slot>/1 to be configured, but an IP address looks like not required.

The section says the interface has to enabled with no shut

see

Enabling the Backplane

The SM-X-1T3/E3 communicates with the host router through an internal Gigabit Ethernet (GE) interface. This GE interface connects to the multi-gigabit fabric (MGF). For the SM to function, the GE interface must be enabled.

Perform this task to enable the GE interface on 2900 and 3900 Series ISRs:

1. enable

2. configure terminal

3. interface sm slot/port

---

Note The backplane is always port 1. /port should always be set to 1.

4. no shut

5. exit

However, in the examples provided later an IP address is configured under the sm1/1 interface

interface Serial1/0

ip address 100.100.100.2 255.255.255.0

dsu bandwidth 44210

!

interface SM1/1

ip address 192.168.2.1 255.255.255.240

no ip proxy-arp

no keepalive

!

But in a previous section it tells that the service module can get an IP address via DHCP.

Information is a little confusing here.

The interface sm <slot>/1 has to be enabled for data traffic to travel between the module and the router.

An IP address provided by DHCP on the router can provide the capability to make a session to the module for troubleshooting purposes.

To be noted the IP address assigned by DHCP is in a VRF, so it should not conflict with same address in other network device (if outer world is reached via the global routing table or VRF default)

I would leave the module to take an IP address from DHCP as it might be useful in the future for troubleshoting.

Hope to help

Giuseppe