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XEN Virtualization Set The MTU For xenbr0 Interface

I've already written about setting the MTU (Maximum Transmission Unit) under Linux including Jumbo frames (FreeBSD specific MTU information is here).

With this quick tip you can increase MTU size to get a better networking performance.
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Linux IPv6 Default Route Not Working

CentOS / Fedora / Red Hat Enterprise / Other Linux distro has weird bug in kernel itself.

I've tested this on Linux 2.6.18-92.1.1.el5 x86_64. The default IPv6 route, as configured in /etc file does not work. You need to add it manually using route command.

# ip route add {IPv-6-IP} dev {device}
OR
# ip route add 2000::/3 dev eth2
Now, you can ping to IPv6 site, enter:
# ping6 ipv6.google.com
Sample output:

PING ipv6.google.com(2001:4860:0:2001::68) 56 data bytes
64 bytes from 2001:4860:0:2001::68: icmp_seq=0 ttl=59 time=37.3 ms
64 bytes from 2001:4860:0:2001::68: icmp_seq=1 ttl=59 time=36.7 ms
64 bytes from 2001:4860:0:2001::68: icmp_seq=2 ttl=59 time=36.9 ms
64 bytes from 2001:4860:0:2001::68: icmp_seq=3 ttl=59 time=36.9 ms

Static routes improves overall performance of your network (especially bandwidth saving). They are also useful in stub networks (i.e. there is only one link to the network). For example, each LAN (located at different offices) is connected to HQ IDC (Internet data center) using single T1/LL/Wan links.

For example under Red Hat/Fedora Linux you can add static router for eth0 network interface by editing /etc/sysconfig/network-scripts/route-eth0 file. Under Debian Linux add static route by editing /etc/network/interface file.

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