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umka69
Tux's lil' helper
Tux's lil' helper


Joined: 31 Mar 2013
Posts: 124

PostPosted: Wed Sep 24, 2014 4:05 pm    Post subject: TUN/TAP networking Reply with quote

Hello.
I'm running several VMs over QEMU. Networking is configured by TUN/TAP devices.
It works but I can't rich one VM from another one.
host ICMP to internet = works
guest1 ICMP to hostnode or internet = works
guest2 ICMP to hostnode or internet = works
guest2 ICMP to guest1 = fails
There are two questions to comuity:
1. How to configurat TUN with /etc/conf.d/net for riching one VM from another?
2. Is TUN/TAP the best way in case of problem?
Configurations of host machine's environment:
Code:
den ~ # cat /etc/conf.d/net
tuntap_tap0="tap"
tuntap_tap1="tap"
config_tap0="null"
config_tap1="null"
config_enp3s0="null"
config_br0="dhcp"
bridge_br0="enp3s0 tap0 tap1"
rc_net_br0_need="net.enp3s0 net.tap0 net.tap1"

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Hu
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Joined: 06 Mar 2007
Posts: 13595

PostPosted: Wed Sep 24, 2014 10:17 pm    Post subject: Reply with quote

Yes, TUN/TAP is a good choice here. What is the nature of the failure? What error messages appear when you try it? Can guest2 communicate with guest1 over any protocol?
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vaxbrat
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Joined: 05 Oct 2005
Posts: 731
Location: DC Burbs

PostPosted: Thu Sep 25, 2014 4:08 am    Post subject: Reply with quote

Check your /etc/sysctl.conf file:

Code:
# Disables packet forwarding
net.ipv4.ip_forward = 0


Should be

Code:

# Enable packet forwarding
net.ipv4.ip_forward = 1


and

Code:
# Ignore ICMP broadcasts
#net.ipv4.icmp_echo_ignore_broadcasts = 1


becomes

Code:
# Don't Ignore ICMP broadcasts
net.ipv4.icmp_echo_ignore_broadcasts = 0


also you want to enable spanning tree protocol on your bridge (stp on) in /etc/conf.d/net

Code:
brctl_br0=( "setfd 0" "sethello 0" "stp on" )
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umka69
Tux's lil' helper
Tux's lil' helper


Joined: 31 Mar 2013
Posts: 124

PostPosted: Fri Sep 26, 2014 5:59 pm    Post subject: Reply with quote

Thx, I did this. The same error after rebooting. :(

HOST configs:
Code:
HOST ~ # cat /etc/sysctl.conf
net.ipv4.ip_forward = 1
net.ipv4.conf.all.rp_filter = 1
net.ipv4.icmp_echo_ignore_broadcasts = 0

HOST ~ # iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

HOST ~ # cat /etc/conf.d/net
tuntap_tap0="tap"
tuntap_tap1="tap"
config_tap0="null"
config_tap1="null"
config_enp3s0="null"
config_br0="dhcp"
# config_br0="192.168.1.1/24"
brctl_br0=( "setfd 0" "sethello 0" "stp on" )
mac_br0="aa:bb:cc:dd:ee:ff"
bridge_br0="enp3s0 tap0 tap1"
rc_net_br0_need="net.enp3s0 net.tap0 net.tap1"


GUEST2 network status
Code:
GUEST2 ~ # ping -c3 192.168.1.9
PING 192.168.1.9 (192.168.1.9) 56(84) bytes of data.
From 192.168.1.7: icmp_seq=1 Destination Host Unreachable
From 192.168.1.7: icmp_seq=2 Destination Host Unreachable
From 192.168.1.7: icmp_seq=3 Destination Host Unreachable
--- 192.168.1.9 ping statistics ---
3 packets transmitted, 0 received, +3 errors, 100% packet loss, time 1999ms
pipe 3
GUEST2 ~ # traceroute 192.168.1.9
traceroute to 192.168.1.9 (192.168.1.9), 30 hops max, 60 byte packets
 1  192.168.1.7 (192.168.1.7)  3005.668 ms !H  3005.640 ms !H  3005.636 ms !H

PS: GUEST2=192.168.1.7 GUEST1=192.168.1.9
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