How can I make my users' browsers use my cache without configuring the browsers for proxying?
First, it is critical to read the full comments in the squid.conf file! That is the only authoritative source for configuration information. However, the following instructions are correct as of this writing (July 1999.)
Getting transparent caching to work requires four distinct steps:
http_port 8080 httpd_accel_host virtual httpd_accel_port 80 httpd_accel_with_proxy on httpd_accel_uses_host_header on
Notes:
First, get and install the IP Filter package.
Put these lines in /etc/ipnat.rules:
# Redirect direct web traffic to local web server.
rdr de0 1.2.3.4/32 port 80 -> 1.2.3.4 port 80 tcp
# Redirect everything else to squid on port 8080
rdr de0 0.0.0.0/0 port 80 -> 1.2.3.4 port 8080 tcp
Modify your startup scripts to enable ipnat. For example, on FreeBSD it looks something like this:
/sbin/modload /lkm/if_ipl.o
/sbin/ipnat -f /etc/ipnat.rules
chgrp nobody /dev/ipnat
chmod 644 /dev/ipnat
Squid-2 (after version beta25) has IP filter support built in. Simple enable it when you run configure:
./configure --enable-ipf-transparent
Add these lines to your squid.conf file:
http_port 8080
httpd_accel_host virtual
httpd_accel_port 80
httpd_accel_with_proxy on
httpd_accel_uses_host_header on
Note, you don't have to use port 8080, but it must match whatever you
used in the /etc/ipnat.rules file.
Patches for Squid-1.X are available from Quinton Dolan's Squid page. Add these lines to squid.conf:
http_port 8080
httpd_accel virtual 80
httpd_accel_with_proxy on
httpd_accel_uses_host_header on
Thanks to Quinton Dolan.
Note: Interception proxying does NOT work with Linux 2.0.30! Linux 2.0.29 is known to work well. If you're using a more recent kernel, like 2.2.X, then you should probably use an ipchains configuration, as described below.
Warning: this technique has some shortcomings.
If you can live with the side-effects, go ahead and compile your kernel with firewalling and redirection support. Here are the important parameters from /usr/src/linux/.config:
#
# Code maturity level options
#
CONFIG_EXPERIMENTAL=y
#
# Networking options
#
CONFIG_FIREWALL=y
# CONFIG_NET_ALIAS is not set
CONFIG_INET=y
CONFIG_IP_FORWARD=y
# CONFIG_IP_MULTICAST is not set
CONFIG_IP_FIREWALL=y
# CONFIG_IP_FIREWALL_VERBOSE is not set
CONFIG_IP_MASQUERADE=y
CONFIG_IP_TRANSPARENT_PROXY=y
CONFIG_IP_ALWAYS_DEFRAG=y
# CONFIG_IP_ACCT is not set
CONFIG_IP_ROUTER=y
You may also need to enable IP Forwarding. One way to do it is to add this line to your startup scripts:
echo 1 > /proc/sys/net/ipv4/ip_forward
Go to the Linux IP Firewall and Accounting page, obtain the source distribution to ipfwadm and install it. Older versions of ipfwadm may not work. You might need at least version 2.3.0. You'll use ipfwadm to setup the redirection rules. I added this rule to the script that runs from /etc/rc.d/rc.inet1 (Slackware) which sets up the interfaces at boot-time. The redirection should be done before any other Input-accept rule. To really make sure it worked I disabled the forwarding (masquerading) I normally do.
/etc/rc.d/rc.firewall:
#!/bin/sh
# rc.firewall Linux kernel firewalling rules
FW=/sbin/ipfwadm
# Flush rules, for testing purposes
for i in I O F # A # If we enabled accounting too
do
${FW} -$i -f
done
# Default policies:
${FW} -I -p rej # Incoming policy: reject (quick error)
${FW} -O -p acc # Output policy: accept
${FW} -F -p den # Forwarding policy: deny
# Input Rules:
# Loopback-interface (local access, eg, to local nameserver):
${FW} -I -a acc -S localhost/32 -D localhost/32
# Local Ethernet-interface:
# Redirect to Squid proxy server:
${FW} -I -a acc -P tcp -D default/0 80 -r 8080
# Accept packets from local network:
${FW} -I -a acc -P all -S localnet/8 -D default/0 -W eth0
# Only required for other types of traffic (FTP, Telnet):
# Forward localnet with masquerading (udp and tcp, no icmp!):
${FW} -F -a m -P tcp -S localnet/8 -D default/0
${FW} -F -a m -P udp -S localnet/8 -D default/0
Here all traffic from the local LAN with any destination gets redirected to the local port 8080. Rules can be viewed like this:
IP firewall input rules, default policy: reject
type prot source destination ports
acc all 127.0.0.1 127.0.0.1 n/a
acc/r tcp 10.0.0.0/8 0.0.0.0/0 * -> 80 => 8080
acc all 10.0.0.0/8 0.0.0.0/0 n/a
acc tcp 0.0.0.0/0 0.0.0.0/0 * -> *
I did some testing on Windows 95 with both Microsoft Internet Explorer 3.01 and Netscape Communicator pre-release and it worked with both browsers with the proxy-settings disabled.
At one time squid seemed to get in a loop when I pointed the browser to the local port 80. But this could be avoided by adding a reject rule for client to this address:
${FW} -I -a rej -P tcp -S localnet/8 -D hostname/32 80
IP firewall input rules, default policy: reject
type prot source destination ports
acc all 127.0.0.1 127.0.0.1 n/a
rej tcp 10.0.0.0/8 10.0.0.1 * -> 80
acc/r tcp 10.0.0.0/8 0.0.0.0/0 * -> 80 => 8080
acc all 10.0.0.0/8 0.0.0.0/0 n/a
acc tcp 0.0.0.0/0 0.0.0.0/0 * -> *
NOTE on resolving names: Instead of just passing the URLs to the proxy server, the browser itself has to resolve the URLs. Make sure the workstations are setup to query a local nameserver, to minimize outgoing traffic.
If you're already running a nameserver at the firewall or proxy server (which is a good idea anyway IMHO) let the workstations use this nameserver.
Additional notes from Richard Ayres
I'm using such a setup. The only issues so far have been that:
- It's fairly useless to use my service providers parent caches (cache-?.www.demon.net) because by proxying squid only sees IP addresses, not host names and demon aren't generally asked for IP addresses by other users;
- Linux kernel 2.0.30 is a no-no as transparent proxying is broken (I use 2.0.29);
- Client browsers must do host name lookups themselves, as they don't know they're using a proxy;
- The Microsoft Network won't authorize its users through a proxy, so I have to specifically *not* redirect those packets (my company is a MSN content provider).
Aside from this, I get a 30-40% hit rate on a 50MB cache for 30-40 users and am quite pleased with the results.
See also Daniel Kiracofe's page.
by Martin Lyons
You need to configure your kernel for ipchains. Configuring Linux kernels is beyond the scope of this FAQ. One way to do it is:
# cd /usr/src/linux
# make menuconfig
The following shows important kernel features to include:
[*] Network firewalls
[ ] Socket Filtering
[*] Unix domain sockets
[*] TCP/IP networking
[ ] IP: multicasting
[ ] IP: advanced router
[ ] IP: kernel level autoconfiguration
[*] IP: firewalling
[ ] IP: firewall packet netlink device
[*] IP: always defragment (required for masquerading)
[*] IP: transparent proxy support
You must include the IP: always defragment, otherwise it prevents you from using the REDIRECT chain.
You can use this script as a template for your own rc.firewall to configure ipchains:
#!/bin/sh
# rc.firewall Linux kernel firewalling rules
# Leon Brooks (leon at brooks dot fdns dot net)
FW=/sbin/ipchains
ADD="$FW -A"
# Flush rules, for testing purposes
for i in I O F # A # If we enabled accounting too
do
${FW} -F $i
done
# Default policies:
${FW} -P input REJECT # Incoming policy: reject (quick error)
${FW} -P output ACCEPT # Output policy: accept
${FW} -P forward DENY # Forwarding policy: deny
# Input Rules:
# Loopback-interface (local access, eg, to local nameserver):
${ADD} input -j ACCEPT -s localhost/32 -d localhost/32
# Local Ethernet-interface:
# Redirect to Squid proxy server:
${ADD} input -p tcp -d 0/0 80 -j REDIRECT 8080
# Accept packets from local network:
${ADD} input -j ACCEPT -s localnet/8 -d 0/0 -i eth0
# Only required for other types of traffic (FTP, Telnet):
# Forward localnet with masquerading (udp and tcp, no icmp!):
${ADD} forward -j MASQ -p tcp -s localnet/8 -d 0/0
${ADD} forward -j MASQ -P udp -s localnet/8 -d 0/0
Also, Andrew Shipton notes that with 2.0.x kernels you don't need to enable packet forwarding, but with the 2.1.x and 2.2.x kernels using ipchains you do. Packet forwarding is enabled with the following command:
echo 1 > /proc/sys/net/ipv4/ip_forward
NOTE: this information comes from Daniel Kiracofe's Transparent Proxy with Squid mini-HOWTO.
You may need to build a new kernel. Be sure to enable all of these options (none of them as modules):
You must say NO to ``Fast switching''
After building the kernel, install it and reboot.
You may need to enable packet forwarding (e.g. in your startup scripts):
echo 1 > /proc/sys/net/ipv4/ip_forward
Use the iptables command to make your kernel intercept HTTP connections and send them to Squid:
iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j REDIRECT --to-port 3128
This works with at least IOS 11.1 and later I guess. Possibly earlier, as I'm no CISCO expert I can't say for sure. If your router is doing anything more complicated that shuffling packets between an ethernet interface and either a serial port or BRI port, then you should work through if this will work for you.
First define a route map with a name of proxy-redirect (name doesn't matter) and specify the next hop to be the machine Squid runs on.
!
route-map proxy-redirect permit 10
match ip address 110
set ip next-hop 203.24.133.2
!
Define an access list to trap HTTP requests. The second line allows
the Squid host direct access so an routing loop is not formed.
By carefully writing your access list as show below, common
cases are found quickly and this can greatly reduce the load on your
router's processor.
!
access-list 110 deny tcp any any neq www
access-list 110 deny tcp host 203.24.133.2 any
access-list 110 permit tcp any any
!
Apply the route map to the ethernet interface.
!
interface Ethernet0
ip policy route-map proxy-redirect
!
Bruce Morgan notes that there is a Cisco bug relating to transparent proxying using IP policy route maps, that causes NFS and other applications to break. Apparently there are two bug reports raised in Cisco, but they are not available for public dissemination.
The problem occurs with o/s packets with more than 1472 data bytes. If you try to ping a host with more than 1472 data bytes across a Cisco interface with the access-lists and ip policy route map, the icmp request will fail. The packet will be fragmented, and the first fragment is checked against the access-list and rejected - it goes the "normal path" as it is an icmp packet - however when the second fragment is checked against the access-list it is accepted (it isn't regarded as an icmp packet), and goes to the action determined by the policy route map!
John notes that you may be able to get around this bug by carefully writing your access lists. If the last/default rule is to permit then this bug would be a problem, but if the last/default rule was to deny then it won't be a problem. I guess fragments, other than the first, don't have the information available to properly policy route them. Normally TCP packets should not be fragmented, at least my network runs an MTU of 1500 everywhere to avoid fragmentation. So this would affect UDP and ICMP traffic only.
Basically, you will have to pick between living with the bug or better performance. This set has better performance, but suffers from the bug:
access-list 110 deny tcp any any neq www
access-list 110 deny tcp host 10.1.2.3 any
access-list 110 permit tcp any any
Conversely, this set has worse performance, but works for all protocols:
access-list 110 deny tcp host 10.1.2.3 any
access-list 110 permit tcp any any eq www
access-list 110 deny tcp any any
Just for kicks, here's an email message posted to squid-users on how to make transparent proxying work with a Cisco router and Squid running on Linux.
by Brian Feeny
Here is how I have Interception proxying working for me, in an environment where my router is a Cisco 2501 running IOS 11.1, and Squid machine is running Linux 2.0.33.
Many thanks to the following individuals and the squid-users list for helping me get redirection and transparent proxying working on my Cisco/Linux box.
First, here is what I added to my Cisco, which is running IOS 11.1. In IOS 11.1 the route-map command is "process switched" as opposed to the faster "fast-switched" route-map which is found in IOS 11.2 and later. You may wish to be running IOS 11.2. I am running 11.1, and have had no problems with my current load of about 150 simultaneous connections to squid.:
!
interface Ethernet0
description To Office Ethernet
ip address 208.206.76.1 255.255.255.0
no ip directed-broadcast
no ip mroute-cache
ip policy route-map proxy-redir
!
access-list 110 deny tcp host 208.206.76.44 any eq www
access-list 110 permit tcp any any eq www
route-map proxy-redir permit 10
match ip address 110
set ip next-hop 208.206.76.44
So basically from above you can see I added the "route-map" declaration, and an access-list, and then turned the route-map on under int e0 "ip policy route-map proxy-redir"
ok, so the Cisco is taken care of at this point. The host above: 208.206.76.44, is the ip number of my squid host.
My squid box runs Linux, so I had to do the following on it:
my kernel (2.0.33) config looks like this:
#
# Networking options
#
CONFIG_FIREWALL=y
# CONFIG_NET_ALIAS is not set
CONFIG_INET=y
CONFIG_IP_FORWARD=y
CONFIG_IP_MULTICAST=y
CONFIG_SYN_COOKIES=y
# CONFIG_RST_COOKIES is not set
CONFIG_IP_FIREWALL=y
# CONFIG_IP_FIREWALL_VERBOSE is not set
CONFIG_IP_MASQUERADE=y
# CONFIG_IP_MASQUERADE_IPAUTOFW is not set
CONFIG_IP_MASQUERADE_ICMP=y
CONFIG_IP_TRANSPARENT_PROXY=y
CONFIG_IP_ALWAYS_DEFRAG=y
# CONFIG_IP_ACCT is not set
CONFIG_IP_ROUTER=y
You will need Firewalling and Transparent Proxy turned on at a minimum.
Then some ipfwadm stuff:
# Accept all on loopback
ipfwadm -I -a accept -W lo
# Accept my own IP, to prevent loops (repeat for each interface/alias)
ipfwadm -I -a accept -P tcp -D 208.206.76.44 80
# Send all traffic destined to port 80 to Squid on port 3128
ipfwadm -I -a accept -P tcp -D 0/0 80 -r 3128
it accepts packets on port 80 (redirected from the Cisco), and redirects them to 3128 which is the port my squid process is sitting on. I put all this in /etc/rc.d/rc.local
I am using v1.1.20 of Squid with Henrik's patch installed. You will want to install this patch if using a setup similar to mine.
I think almost everyone who have tried to build a transparent proxy setup have been bitten by this one.
Measures you can take:
by Duane Wessels
I set out yesterday to make transparent caching work with Squid and FreeBSD. It was, uh, fun.
It was relatively easy to configure a cisco to divert port 80 packets to my FreeBSD box. Configuration goes something like this:
access-list 110 deny tcp host 10.0.3.22 any eq www access-list 110 permit tcp any any eq www route-map proxy-redirect permit 10 match ip address 110 set ip next-hop 10.0.3.22 int eth2/0 ip policy route-map proxy-redirectHere, 10.0.3.22 is the IP address of the FreeBSD cache machine.
Once I have packets going to the FreeBSD box, I need to get the kernel to deliver them to Squid. I started on FreeBSD-2.2.7, and then downloaded IPFilter. This was a dead end for me. The IPFilter distribution includes patches to the FreeBSD kernel sources, but many of these had conflicts. Then I noticed that the IPFilter page says ``It comes as a part of [FreeBSD-2.2 and later].'' Fair enough. Unfortunately, you can't hijack connections with the FreeBSD-2.2.X IPFIREWALL code (ipfw), and you can't (or at least I couldn't) do it with natd either.
FreeBSD-3.0 has much better support for connection hijacking, so I suggest you start with that. You need to build a kernel with the following options:
options IPFIREWALL
options IPFIREWALL_FORWARD
Next, its time to configure the IP firewall rules with ipfw. By default, there are no "allow" rules and all packets are denied. I added these commands to /etc/rc.local just to be able to use the machine on my network:
ipfw add 60000 allow all from any to any
But we're still not hijacking connections. To accomplish that,
add these rules:
ipfw add 49 allow tcp from 10.0.3.22 to any
ipfw add 50 fwd 127.0.0.1 tcp from any to any 80
The second line (rule 50) is the one which hijacks the connection.
The first line makes sure we never hit rule 50 for traffic originated
by the local machine. This prevents forwarding loops.
Note that I am not changing the port number here. That is, port 80 packets are simply diverted to Squid on port 80. My Squid configuration is:
http_port 80
httpd_accel_host virtual
httpd_accel_port 80
httpd_accel_with_proxy on
httpd_accel_uses_host_header on
If you don't want Squid to listen on port 80 (because that requires root privileges) then you can use another port. In that case your ipfw redirect rule looks like:
ipfw add 50 fwd 127.0.0.1,3128 tcp from any to any 80
and the squid.conf lines are:
http_port 3128
httpd_accel_host virtual
httpd_accel_port 80
httpd_accel_with_proxy on
httpd_accel_uses_host_header on
This is to do with configuring transparent proxy for an ACC Tigris digital access server (like a CISCO 5200/5300 or an Ascend MAX 4000). I've found that doing this in the NAS reduces traffic on the LAN and reduces processing load on the CISCO. The Tigris has ample CPU for filtering.
Step 1 is to create filters that allow local traffic to pass. Add as many as needed for all of your address ranges.
ADD PROFILE IP FILTER ENTRY local1 INPUT 10.0.3.0 255.255.255.0 0.0.0.0 0.0.0.0 NORMAL
ADD PROFILE IP FILTER ENTRY local2 INPUT 10.0.4.0 255.255.255.0 0.0.0.0 0.0.0.0 NORMAL
Step 2 is to create a filter to trap port 80 traffic.
ADD PROFILE IP FILTER ENTRY http INPUT 0.0.0.0 0.0.0.0 0.0.0.0 0.0.0.0 = 0x6 D= 80 NORMAL
Step 3 is to set the "APPLICATION_ID" on port 80 traffic to 80. This causes all packets matching this filter to have ID 80 instead of the default ID of 0.
SET PROFILE IP FILTER APPLICATION_ID http 80
Step 4 is to create a special route that is used for packets with "APPLICATION_ID" set to 80. The routing engine uses the ID to select which routes to use.
ADD IP ROUTE ENTRY 0.0.0.0 0.0.0.0 PROXY-IP 1
SET IP ROUTE APPLICATION_ID 0.0.0.0 0.0.0.0 PROXY-IP 80
Step 5 is to bind everything to a filter ID called transproxy. List all local filters first and the http one last.
ADD PROFILE ENTRY transproxy local1 local2 http
With this in place use your RADIUS server to send back the ``Framed-Filter-Id = transproxy'' key/value pair to the NAS.
You can check if the filter is being assigned to logins with the following command:
display profile port table
Fyodor has tracked down the cause of unusual ``connection reset by peer'' messages when using Cisco policy routing to hijack HTTP requests.
When the network link between router and the cache goes down for just a moment, the packets that are supposed to be redirected are instead sent out the default route. If this happens, a TCP ACK from the client host may be sent to the origin server, instead of being diverted to the cache. The origin server, upon receiving an unexpected ACK packet, sends a TCP RESET back to the client, which aborts the client's request.
To work around this problem, you can install a static route to the null0 interface for the cache address with a higher metric (lower precedence), such as 250. Then, when the link goes down, packets from the client just get dropped instead of sent out the default route. For example, if 1.2.3.4 is the IP address of your Squid cache, you may add:
ip route 1.2.3.4 255.255.255.255 Null0 250
This appears to cause the correct behaviour.
Contributors: Glenn Chisholm and Lincoln Dale.
CISCO's Web Cache Coordination Protocol V1.0 is supported in squid 2.3 and later. support WCCP V2.0. Now that WCCP V2 is an open protocol, Squid may be able to support it in the future.
There are two different methods of configuring WCCP on CISCO routers. The first method is for routers that only support V1.0 of the protocol. The second is for routers that support both.
It is possible that later versions of IOS 11.x will support V2.0 of the protocol. If that is the case follow the 12.x instructions. Several people have reported that the squid implimentation of WCCP does not work with their 11.x routers. If you experience this please mail the debug output from your router to squid-bugs.
conf t
wccp enable
!
interface [Interface Carrying Outgoing Traffic]x/x
!
ip wccp web-cache redirect
!
CTRL Z
write mem
Some of the early versions of 12.x do not have the 'ip wccp version' command. You will need to upgrade your IOS version to use V1.0.
You will need to be running at least IOS Software Release 12.0(5)T if you're running the 12.0 T-train. IOS Software Releases 12.0(3)T and 12.0(4)T do not have WCCPv1, but 12.0(5)T does.
conf t
ip wccp version 1
ip wccp web-cache
!
interface [Interface Carrying Outgoing/Incomming Traffic]x/x
ip wccp web-cache redirect out|in
!
CTRL Z
write mem
Some people report problems with WCCP and IOS 12.3. They see truncated or fragmented GRE packets arriving at the cache. Apparently it works if you disable Cisco Express Forwarding for the interface:
conf t ip cep # some systems may need 'ip cep global' int Ethernet0/0 no ip route-cache cef CTRL Z
FreeBSD first needs to be configured to recieve and strip the GRE encapsulation from the packets from the router. To do this you will need to patch and recompile your kernel.
First, a patch needs to be applied to your kernel for GRE support. Apply the patch for FreeBSD-3.x kernels or the patch for FreeBSD-4.x kernels as appropriate.
Secondly you will need to download gre.c for FreeBSD-3.x or gre.c for FreeBSD-4.x and copy it to /usr/src/sys/netinet/gre.c.
Finally add "OPTION GRE" to your kernel config file and rebuild your kernel. Note, the opt_gre.h file is created when you run config. Once your kernel is installed you will need to configure FreeBSD for transparent proxying.
Al Blake has written a Cookbook for setting up transparent WCCP using Squid on RedHat Linux and a cisco access server.
There are currently two methods for supporting WCCP with Linux 2.2. A specific purpose module. Or the standard Linux GRE tunneling driver. People have reported difficulty with the standard GRE tunneling driver, however it does allow GRE functionality other than WCCP. You should choose the method that suits your enviroment.
Linux 2.2 kernels already support GRE, as long as the GRE module is compiled into the kernel.
You will need to patch the ip_gre.c code that comes with your Linux kernel with this patch supplied by Jan Haluza.
Ensure that the GRE code is either built as static or as a module by chosing the appropriate option in your kernel config. Then rebuild your kernel. If it is a module you will need to:
modprobe ip_gre
The next step is to tell Linux to establish an IP tunnel between the router and your host. Daniele Orlandi reports that you have to give the gre1 interface an address, but any old address seems to work.
iptunnel add gre1 mode gre remote <Router-IP> local <Host-IP> dev <interface>
ifconfig gre1 127.0.0.2 up
<Router-IP> is the IP address of your router that is intercepting the
HTTP packets. <Host-IP> is the IP address of your cache, and
<interface> is the network interface that receives those packets (probably eth0).
Joe Cooper has a patch for Linux 2.2.18 kernel on his Squid page.
This module is not part of the standard Linux distributon. It needs to be compiled as a module and loaded on your system to function. Do not attempt to build this in as a static part of your kernel.
Download the Linux WCCP module and compile it as you would any Linux network module.
Copy the module to /lib/modules/kernel-version/ipv4/ip_wccp.o. Edit /lib/modules/kernel-version/modules.dep and add:
/lib/modules/kernel-version/ipv4/ip_wccp.o:
Finally you will need to load the module:
modprobe ip_wccp
The machine should now be striping the GRE encapsulation from any packets recieved and requeuing them. The system will also need to be configured for transparent proxying, either with ipfwadm or with ipchains.
If you have managed to configuring your operating system to support WCCP with Squid please contact us with the details so we may share them with others.
IOS releases:
Cisco has published WCCPv2 as an Internet Draft (expires Jan 2001). At this point, Squid does not support WCCPv2, but anyone is welcome to code it up and contribute to the Squid project.
by Brian Feeny.
First, configure Squid for transparent caching as detailed at the beginning of this section.
Next, configure the Foundry layer 4 switch to transparently redirect traffic to your Squid box or boxes. By default, the Foundry redirects to port 80 of your squid box. This can be changed to a different port if needed, but won't be covered here.
In addition, the switch does a "health check" of the port to make sure your squid is answering. If you squid does not answer, the switch defaults to sending traffic directly thru instead of redirecting it. When the Squid comes back up, it begins redirecting once again.
This example assumes you have two squid caches:
squid1.foo.com 192.168.1.10 squid2.foo.com 192.168.1.11
We will assume you have various workstations, customers, etc, plugged into the switch for which you want them to be transparently proxied. The squid caches themselves should be plugged into the switch as well. Only the interface that the router is connected to is important. Where you put the squid caches or other connections does not matter.
This example assumes your router is plugged into interface 17 of the switch. If not, adjust the following commands accordingly.
telnet@ServerIron#conf t
telnet@ServerIron(config)# server cache-name squid1 192.168.1.10 telnet@ServerIron(config)# server cache-name squid2 192.168.1.11
telnet@ServerIron(config)#server cache-group 1 telnet@ServerIron(config-tc-1)#cache-name squid1 telnet@ServerIron(config-tc-1)#cache-name squid2
telnet@ServerIron(config)# ip policy 1 cache tcp http local
telnet@ServerIron(config)#int e 17 telnet@ServerIron(config-if-17)# ip-policy 1
Since all outbound traffic to the Internet goes out interface 17 (the router), and interface 17 has the caching policy applied to it, HTTP traffic is going to be intercepted and redirected to the caches you have configured.
The default port to redirect to can be changed. The load balancing algorithm used can be changed (Least Used, Round Robin, etc). Ports can be exempted from caching if needed. Access Lists can be applied so that only certain source IP Addresses are redirected, etc. This information was left out of this document since this was just a quick howto that would apply for most people, not meant to be a comprehensive manual of how to configure a Foundry switch. I can however revise this with any information necessary if people feel it should be included.