I've installed F14 on KVM using bridged networking between my host device eth1 and guest device eth0. I manually added the bridge by editing my /etc/sysconfig/network-scripts/ifcfg-eth1 and ifcfg-br0(name I gave the bridge). When I run the virtual machine and enable the eth0 device on the guest, it works completely fine, however, my host eth0 device has extremely limited bandwidth and isn't usable. I tried shutting down the KVM machine, and the host eth0 still wasn't usable. It does however retain it's use if I reboot the physical machine, which also for some reason deletes my ifcfg-br0 bridge file in /etc/sysconfig/network-scripts/ . I am now lost,lol.

if you set up a bridge br0 on eth0, the bridge should be configured with an IP and the eth0 is only there as the physical device.
In general, VM running or not, br0 becomes the hosts' working NIC.

If you see network degradation after that, you need to troubleshoot the NIC, I doubt kvm has anything to do with that

The thing that was confusing me was that I have two pyhsical NICs both cable connected to a switch so even if I have one bound to the VM shouldn't the other still maintain a connection. It's connected, it's just REALLY slow.