Recently I’ve been doing more on Alcatel as I’m working in O2’s test-bed down in Slough, slaving away at testing aspects of their new LLU broadband core and new BT 21CN wholesale connectivity. Although I’ve not been able to write a lot in recent years due working for an integrator rather than an ISP; I’m mostly not allowed or it’s unwise for me to divulge what I’m working on…

However, it’s common knowledge that many providers use Alcatel and they seem to do pretty well in the ‘booming’ broadband market. Hence I thought I’d share a little snippet of an annoyance I recently encountered.

When using an Alcatel 7210 to sniff traffic and interconnect different media; 1Gbps copper and 10Gbps fibre. I found that sniffing is counter intuitive to people only trained on Cisco. A few pointers:

1. Port mirror destinations are defined in configuration
2. Port mirror sources are set through debug commands
3. When mirroring VPLS ports (I needed an e-pipe/Layer-2 tunnel) I found that egress sources did not work, only ingress did and only one ingress port can be set per mirror session. It did not matter if I use the port or the SAP as source.

I was left to sniff in two places to capture both up- & down-stream traffic. YMMV as a 7750 will be different, but I don’t have one available to me to test on…

Commands used:

#--------------------------------------------------
echo "Mirror Configuration"
#--------------------------------------------------
  mirror
    mirror-dest 4 create
      sap 1/1/4 create
      exit
      no shutdown
    exit
    mirror-dest 11 create
      sap 1/1/11 create
      exit
      no shutdown
    exit
  exit

And the debug command:

*A:<hostname># debug mirror-source 4 port ?
- no port ...
- port <port-id> egress ingress
- port <port-id> egress
- port <port-id> ingress
- port lag ...

*A:<hostname># debug mirror-source 4 sap ?
- no sap <sap-id> [ingress]
- sap <sap-id> {[ingress] }

As can be seen above capturing by SAP is only supported at ingress. Using port and SAP yielded the same result, only ingress packets were ever sent to the destination port. Despite show mirror stating both Egr & Ing.

*A:<hostname># show mirror mirror-dest 11

===============================================================================
Mirror Service
===============================================================================
Service Id       : 11                   Type          : Ether
Description      : (Not Specified)
Admin State      : Up                   Oper State    : Up
Forwarding Class : be                   Remote Sources: No
Slice            : 0
Destination SAP  : 1/1/11               Egr QoS Policy: 1

-------------------------------------------------------------------------------
Local Sources
-------------------------------------------------------------------------------
Admin State      : Up

-Port                                   1/1/26                          Egr Ing
===============================================================================

Tags: 7210,Alcatel,port mirroring,port span
Categories: Networking, Work
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