Problem with Cloud0

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matrixritter
Posts: 2
Joined: Sun Feb 18, 2018 9:06 pm

Problem with Cloud0

Post by matrixritter » Sun Feb 18, 2018 9:44 pm

Hello my fellow network engineers,

I struggle to connect my VMs to my external network via the cloud0 bridge. So far, the VMs start fine and can be connected to cloud0.

1) brctl confirms this:

root@eve-ng:~# brctl show pnet0
bridge name bridge id STP enabled interfaces
pnet0 8000.005056123456 no eth0
vunl0_5_0
vunl0_8_0
vunl0_9_0

2) I focus on vunl0_9_0 (keep an eye on the MAC address):

root@eve-ng:~# ip link show vunl0_9_0
15: vunl0_9_0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc pfifo_fast master pnet0 state UP mode DEFAULT group default qlen 1000
link/ether 16:92:5b:be:4b:ce brd ff:ff:ff:ff:ff:ff

When I sniffed the eth0 interface for DHCP requests and replies I found this:

root@eve-ng:~# tcpdump -i eth0 -n -e 'udp port 67 and udp port 68'
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
23:30:00.277404 00:50:00:00:09:00 > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 342: 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 00:50:00:00:09:00, length 300
23:30:00.277652 00:50:00:00:09:00 > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 342: 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 00:50:00:00:09:00, length 300
23:30:00.282293 50:06:04:85:56:44 > 00:50:00:00:09:00, ethertype IPv4 (0x0800), length 344: 10.60.60.1.67 > 10.60.60.74.68: BOOTP/DHCP, Reply, length 302

00:50:00:00:09:00 is the MAC from inside the VM and created through QEMU :o :

root@eve-ng:~# ps aux | grep vunl0_9_0
root 6389 0.0 0.0 6424 1328 ? S Feb16 0:00 /opt/unetlab/wrappers/qemu_wrapper -T 0 -D 9 -t Linux -F /opt/qemu/bin/qemu-system-x86_64 -d 0 -x -- -device e1000,netdev=net0,mac=00:50:00:00:09:00 -netdev tap,id=net0,ifname=vunl0_9_0,script=no -smp 1 -m 2048 -name Linux -uuid afef4c90-45a0-4ac6-be03-ef42a94c96a4 -vnc :26877 -hda hda.qcow2 -machine type=pc-1.0,accel=kvm -vga std -usbdevice tablet -boot order=dc

Sniffing vunl0_9_0 shows no replies, so I guess the DHCP replies are dropped at bridge level. The VM itself never gets an address. Can anybody explain to me, why there are two different mac addresses involved and not one?

And finally: How to make this work?

matrixritter
Posts: 2
Joined: Sun Feb 18, 2018 9:06 pm

Re: Problem with Cloud0

Post by matrixritter » Sun Feb 18, 2018 9:55 pm

I discussed the issue on the chat and I need to check if promiscous mode is enabled (I guess it's not).

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