Re: VLAN and bridging with xen

----- Original Message ----- 
From: "Greg Brackley" <[email protected]>
> In the past I have tried an e1000 driver (As the machine also has a dual 
> pro/1000 mt card in it), and not had any success. I'll try it again.

I switched over to using the Intel PRO/1000 dual MT port.  I noticed two 
things.

1. I could get pings of size 1472 through (c.f. 1460 with the sk-9e22 port)

2. I setup a 'dig slashdot.org' to loop around and generate a constant UDP 
packet stream. A tcpdump on the next hop was getting the UDP packets, but 
they appeared to have a bad checksum. A tcpdump of the packets as they left 
the VLAN interface said the checksum was ok. I tried turning off (and then 
back on) tx and rx checksum support, but didn't see any change (would this 
change automagically propagate through the stack, or do I need to pull 
everything down).

Is this a real checksum error or a phantom bad checksum?

Greg.


----- dump of eth3 (which the VLAN interface is on) ----------
# tcpdump -i eth3.148 -n -vv
20:07:21.461176 arp who-has 192.168.148.254 tell 192.168.148.1
20:07:21.461259 IP (tos 0x0, ttl  64, id 2, offset 0, flags [DF], proto 17, 
length: 58) 192.168.148.1.32828 > 192.168.134.6.domain: [udp sum ok]  25138+ 
A? slashdot.org. (30)

# tcpdump -i eth3 -n -vv
tcpdump: WARNING: eth3: no IPv4 address assigned
tcpdump: listening on eth3, link-type EN10MB (Ethernet), capture size 96 
bytes
20:11:16.503715 IP (tos 0x0, ttl  64, id 0, offset 0, flags [DF], proto 17, 
length: 58) 192.168.148.1.32828 > 192.168.134.6.domain: [udp sum ok]  14858+ 
A? slashdot.org. (30)

----- dump from the next hop machine 192.168.148.254----------
# tcpdump -i bond0.148 -n -vv
20:08:42.522754 arp who-has 192.168.148.254 tell 192.168.148.1
20:08:42.522762 arp reply 192.168.148.254 is-at 00:12:3f:20:69:f0
20:08:42.542368 IP (tos 0x0, ttl  64, id 0, offset 0, flags [DF], proto 17, 
length: 58) 192.168.148.1.32828 > 192.168.134.6.domain: [bad udp cksum 
b608!]  42859+ A? slashdot.org. (30)