Re: Two squids on the same cache?

From: Dirk Lutzebaeck <>
Date: Tue, 27 Aug 1996 11:58:16 +0200

Hello Ira,

Ira Abramov writes:
> On Mon, 26 Aug 1996, Dirk Lutzebaeck wrote:
> > > > I want to run two squids on the same machine which use different
> > > > routes. Is it possible that both work on the same cache directory?
> > >
> > > myguess is not, because most/all of the meta info is floating in the RAM,
> > > in the process' protected memory, I guess it is safe to guess the two
> > > processes won't share this memory either... why on earth would you want to
> > > run two squids on the same machine? it won't be more efficient, that's for
> > > sure! get another el-cheapo pentium platform for $1500 or less and run a
> > > neighbour!
> >
> > Well, the problem is that our Intranet is behind a firewall. We have
> > two IP provider using dynamic IP allocation via PPP on two ISDN
> > lines. I want to run two squids on the proxy/cache machine which
> > leaves the user to choose the IP provider route via a proxy definition
> > in Netscape. Obviously the two squid should share the cache. At the
> > moment I have no plausible solution to it.
> woooooww... weird setup!


> A. two dynamic IPs connected at the same time? and how do you decide which
> one to route out from?!

Hopefully one squid takes his own route by using tcp_outgoing_address
I suppose.

> B. why should the user/squid care about how the routing takes place?

Because both providers have different links from Europe to the US (our
site is in Europe). If you can't reach a site in the US due to net
overload, take the other proxy. That's up to the user.

> let me get it righ, will this be a right drawing of your net?
> ----- -----
> \ /
> \ /
> ( ISDN switch - telco)
> |
> |
> |
> | BRI into the LAN (router? card in PC? in server?)
> [_] router
> |
> [_] firewall, also running squid
> |
> | rest of the LAN
> ------------------
> so far so good?

Not quite. The ISDN switch is a LINUX box which is the firewall and
the proxy/cache host at the same time:

   ----- -----
     \ /
      \ /
       \ /
        \ /
 (Linux ISDN/Router/Firewall running two squids neighboring each other)
              | LAN
         (Sun Server)
      | | | | | | |
      | | | | | | |

> now, I understand you sometime connect through one ISP, sometimes through
> the other, but also sometimews through both? how do you handle the
> routing? RIP2?

I want to connect to both ISPs at the same time. I thought the default
route goes to ISPA and the other route is explicitley used by the
other squid using tcp_outgoing_addr in the conf. I tried it. It
doesn't work :( The system comes back with the message "Can't assign
requested address". Probably the IP address to ISPB (which is pingable
also when connected to ISPA by the way!) can't be reached by squid
using tcp_outgoing_addr.

> since you say the squid the user uses dictates the link through which he
> will exit to the WAN, and I suppose the squid doesn't source-route
> requests,

What do you mean by source-route requests? tcp_outgoing_addr?

> in that case, you still have no problem with one squid on your
> LAN (fw?) that has two neighbours to ask for cache,

Yes, tried this.

> but the router's
> routing table will define through which line it should go if the requested
> item is in neither.

Now, Duane can you tell me exactly what tcp_outgoing_addr does???

> in any case, two squids on the same machine make little sense, but if I am
> missing something here and you MUST have two squids up, I guess they could
> sit on different ports and treat eachother as neighbours, and thus
> cooperate with the cahing, but not use the same actual cache on the
> disk...


Thanks for your help,

Received on Tue Aug 27 1996 - 02:51:44 MDT

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