GRE Tunnels

[ahtivak]

Hi ,

I am trying to set up a GRE tunnel between two linux routers. The routers have a 400 MHz Processor.

Linux .2 65.0.0.2 Linux
LAN1 -------- Router -------- INTERNET ---- Router ---- LAN2
10.10.10.0 .1 208.1.0.1 (Simulated) .1 .1 192.168.2.0/24
/24


Scripts to Create the tunnel

ip tunnel add tun0 mode gre remote 65.0.0.1 local 208.1.0.1 dev eth1 ttl 255
ip addr add 192.18.0.1 dev tun0
ip route add 192.18.0.2 dev tun0
ip route add 192.168.2.0/24 dev tun0

I change the remote and local ip and setup the tunnel ad the other end.

The tunnel is up and i am able to send data through the tunnel. But its very slow. Without the tunnels i could send 50Mbps and with the tunnels its aroud 1-2 Mbps.


--- Kernel Config --- --
CONFIG_NETFILTER=y
# CONFIG_NETFILTER_DEBUG is not set
# CONFIG_FILTER is not set
CONFIG_UNIX=y
CONFIG_INET=y
CONFIG_IP_MULTICAST=y
CONFIG_IP_ADVANCED_ROUTER=y
CONFIG_IP_MULTIPLE_TABLES=y
CONFIG_IP_ROUTE_FWMARK=y
CONFIG_IP_ROUTE_NAT=y
CONFIG_IP_ROUTE_MULTIPATH=y
CONFIG_IP_ROUTE_MULTIPATH_SEQUENTIAL=y
CONFIG_IP_ROUTE_TOS=y
# CONFIG_IP_ROUTE_VERBOSE is not set
# CONFIG_IP_PNP is not set
# CONFIG_NET_ARP_LIMIT is not set
# CONFIG_NET_IPIP is not set
CONFIG_NET_IPGRE=y
# CONFIG_NET_IPGRE_BROADCAST is not set
# CONFIG_IP_MROUTE is not set
# CONFIG_ARPD is not set

------------------------------------------------------

Any ideas to tune up the tunnel performance would be greatly Appreciated.

Thanks,
Kavitha

 

[TrojanWarBlade]

Sorry, I have no ideas to help you but we'd all appreciate it if you post any solutions you find.

Good Luck!



Trojan.

 

[normntwrk]

It's possible that with the tunnel that your MTU value may be too high which will fragment the packets.

You should be able to check this by pinging something on the other end of the tunnel with large packets and work your way down to where it works
ping xxx.xxx.xxx.xxx -s 1500 (-s 1500 = size of packet)
ping xxx.xxx.xxx.xxx -s 1460
and so on...if it shows an issue you will probably need to adjust the MTU value on both ends

It could be the CPU isn't up to the task, tunneling is very CPU intensive..check with top to watch CPU

There is a chapter from a book available here which may help

http://web10.eppg.com/betabooks/oct01/mairs/ch10.html

Norm