Tutorials Thread

Looks pretty interesting even though I've just had a quick glance over the first couple of pages. I've been thinking of creating a stick thread with a few tutorials in it (I know I promised some people a file sharing tutorial a while back but other things got in the way).

Would you have any objection to me changing the title of this thread and stickying it and perhaps adding to it over time Webmonkey?

My Windows Vista File Sharing Tutorial:

Sorry about to delay to the people I mentioned it to.

This thread is to be used to post tutorials, anyone can contribute as long as it's relevant to Nets & Comms.

Ok, something a little...different here. I've a spare 30 mins this morning, so I thought i'd throw up a quick howto on WCCP!

WCCP is like automated/load balancing PBR (Policy Based Routing), and it's a Cisco protocol, but it's open (Squid proxy supports WCCP, as does Bluecoat). A quick Wikipedia link is here: WCCP. I apologise that this will be a Cisco specific guide!

WCCP is used to transparently intercept certain types of traffic, and redirect to another device. A typical use case for WCCP would be connecting a proxy to the network. Instead of configuring the proxy's IP on *every* host PC, you just use WCCP interception at the switch, and traffic gets redirected transparently to the user. This is quite useful for installing a transparent 'cache farm' in a larger enterprise/ISP to cut down on bandwidth costs.

WCCP uses both L2 or GRE to get traffic to/from the switch. L2 is just a re-write of the src/dst mac addresses, whereas GRE is where you encapsulate the original packet in a new IP packet.

Differences (brief):
L2-consumes less CPU (if not supposed via CEF/fastpath). But needs to be on the same subnet (ie: cant cross L3)
GRE-can span multiple L3 hops. Consumes more CPU on switch.

WCCP uses service groups to redirect traffic from multiple vlans/multiple directions. You can use service group 0 - 99 or web-cache.

You need two things when configuring WCCP,
* A switch which supports WCCP. I'm using a Cat 6k, Sup720 running 12.2(33)SXF8. This has an interface in vlan 499, IP address 192.168.231.1
* A 'client' device (usually a web proxy). I'll be using an ACNS, running 5.5.9. This has it's Gig1/0 in vlan 499, IP address does not matter

Topology:

Vlan 500 --> Router 
                   |
                   |
            Vlan 499 --> ACNS --> Internet 

Vlan

Steps:
1) Configure your service groups

Router>en
Router#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#ip wccp ?
  <0-99>     Dynamically defined service identifier number
  version    protocol version
  web-cache  Standard web caching service

Router(config)#ip wccp web-cache ?
  accelerated    Enable hardware acceleration
  group-address  Set the multicast group
  group-list     Set the access-list used to permit group membership
  password       Authentication password (key)
  redirect-list  Set the access-list used to permit redirection
  <cr>

Router(config)#ip wccp web-cache
Router(config)#ip wccp version 2

So in the above example, I've enabled the the web-cache (ie: port 80) service on the switch 'Router' , then finally I enabled WCCP via the 'ip wccp ver 2' command.

2) Now I'm going to redirect traffic from vlan 500

Router# conf t
Router(config)# inter vlan 500
Router(config-if)#ip wccp web-cache redirect in

3) Next up, I'm going to configure a client. This client is a proxy (Cisco ACNS)

ACNS#conf t
ACNS(config)# wccp router-list 1 192.168.231.1
ACNS(config)# wccp web-cache router-list-num 1 ?
  assign-method-strict  Use configured assignment method only.
  l2-redirect           Packet forwarding by Layer 2 redirect
  l2-return             Packet return by Layer 2 rewrite
  mask-assign           Use the mask method for CE assignment
  password              Authentication password (key)
  weight                Assignment weight
  <cr>
ACNS(config)# wccp web-cache router-list-num 1 
ACNS(config)# wccp version 2

So what I'm doing here is first defining a list of switches 'router-list' which we want to register against.
Next up I'm telling the ACNS to use the web-cache service group to register against this router list (notice the extra options I did not use), and finally, I'm running WCCP with the 'wccp ver 2' command.


4) Verify packets are being redirected:
On the ACNS:

ACNS#sh wccp gre
Transparent non-GRE packets received:       17626
Total packets accepted:                     17626

A lot of output was removed there, but the two listed counters should be incrementing over time.

On the Switch:

cdn-2811-1#sh ip wccp
Global WCCP information:
    Router information:
        Router Identifier:                   -not yet determined-
        Protocol Version:                    2.0

    Service Identifier: 62
        Number of Service Group Clients:     0
        Number of Service Group Routers:     0
        Total Packets s/w Redirected:        0
          Process:                           0
          Fast:                              0
          CEF:                               0

Obviously, these packets *should* increment on the switch too, but a word of warnining: on the 6k, if WCCP is CEF accelerated, the sh ip wccp counters are not supported

And finally, troubleshooting!

You can use tethereal on the CLI of the ACNS:

ACNS#tethereal -R "wccp" 

What to look for:
HERE_I_AM and I_SEE_YOU messages, wireshark can decode these somewhat. Also check that all buckets are assigned (you can expand the packet in wireshark, you're looking for all 1's or F's)

Um, think that's about it! If anything is unclear, just give me a shout!
Regards,

Ok like I said in the other thread it is indeed quick and dirty and doesn't go into a huge amount of detail. It's a brief explanation of the GUI and a run through doing a basic trace and then a trace using capture filters. Does anyone have anything else they'd like covered in particular when it comes to Wireshark?

If so either post here or drop me a PM and I'll see what I can do.

Had a copy of it saved myself so here it is.

Great,Thanks Lads