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I have a KVM on Ubuntu as a home server. My gateway is a VM with WAN interface connected to the bridge configured as

auto eth1
iface eth1 inet manual

auto br1
iface br1 inet manual
    bridge_ports eth1
    bridge_stp off
    bridge_fd 0
    bridge_maxwait 0

Ethernet cable from my ISP is connected to eth1. I wasn't able to find proper network configuration for this scenario. Can evil people get access to my host through this interface? I have no nuclear secrets here, but anyway.

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migrated from serverfault.com Jul 13 '10 at 22:49

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1 Answer

up vote 2 down vote accepted

This probably depends on your ISP and what type of connection you have, but if you don't have an IP configured, you are probably pretty safe. If your ISP happens to allow other protocols down the wire (most don't), then you might be vulnerable through one of them, if it were configured.

EDIT: To answer the question in the comments, I believe ifconfig will show you what protocols are on a NIC (someone please chime in if you think otherwise). Notice that I've got IPV4 (inet) and IPV6 (inet6) on mine:

root@INFRA:~# ifconfig eth0 
eth0      Link encap:Ethernet  HWaddr 00:0c:29:aa:bb:cc  
          inet addr:10.X.X.2  Bcast:10.X.X.255  Mask:255.255.255.0
          inet6 addr: fe80::aaa:fff:ddd:bbbb/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:46403049 errors:0 dropped:0 overruns:0 frame:0
          TX packets:54127522 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:16294573928 (16.2 GB)  TX bytes:52118956524 (52.1 GB)
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My gateway VM gets IP address through DHCP from my ISP. How can I check if other protocols (which?) are configured? –  Art Shayderov Jul 13 '10 at 19:37
2  
There are a variety of layer 2 protocols that are still usable on an IP-less network interface. However, those are very unlikely to be around on a residential ISP connection. –  SysAdmin1138 Jul 13 '10 at 21:18
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