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Re: [lvs-users] LVS-DR generates TONS of icmp unreachables

To: Wensong Zhang <wensong@xxxxxxxxxxxx>
Subject: Re: [lvs-users] LVS-DR generates TONS of icmp unreachables
Cc: Jivko Velev <jiko@xxxxxxxxxx>, Jerry Glomph Black <black@xxxxxxxx>, Julian Anastasov <uli@xxxxxxxxxxxxxxxxxxxxxx>, lvs-users@xxxxxxxxxxxxxxxxxxxxxx
From: Joseph Mack <mack@xxxxxxxxxxx>
Date: Sat, 22 Jan 2000 12:08:06 -0500 (EST)
On Sun, 23 Jan 2000, Wensong Zhang wrote:

> > If the client goes down after the connection is established, where do the
> > dest_unreachable icmp packets generated by the last router go?
> 
> If the client is unreachable, some router will generate an
> ICMP_DEST_UNREACH packet and sent to the VIP, then the director will
> forward the ICMP packet to the real server.
> 
> > 
> > Since icmp packets are udp, are the icmp packets routed through the
> > director independantly of the services that are being LVS'ed. ie if the
> > director is only forwarding port 80/tcp, from CIP to a particular RIP,
> > does the LVS code which handles the icmp forward all icmp packets from the
> > CIP to that RIP. What if the client has a telnet session to one realserver
> > and http to another realserver?
> > 
> 
> It doesn't matter, because the header of the original packet is
> encapsulated in the icmp packet. It is easy to identify which
> connection is the icmp packet for.

If the client has two connections to the LVS (say telnet and http)
each to 2 different realservers and the client goes down, the director
gets 2 ICMP_DEST_UNREACH packets. The director knows from the CIP:port
which realserver to send the icmp packet to?


> P.S. I will go home today for a three-week winter vacation. Since the
> Spring Festival is a great time for family reunion in China, 

Spring is in January in China? We're having snow here :-)
 
Have fun

Joe

--
Joseph Mack mack@xxxxxxxxxxx

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