Last clearing of "show interface" counters 04:53:18 Output flow-control is XON, input flow-control is XON Hardware is PQ3_TSEC, address is 982 (bia 982) GigabitEthernet0/2 is up, line protocol is up Loopback3 10.250.230.204 YES manual up upĭescription Router Integrity Enterprise Template rollout for BOA AUDIT Feb 2005 GigabitEthernet0/2 10.251.63.9 YES NVRAM up up GigabitEthernet0/0 unassigned YES NVRAM administratively down down Interface IP-Address OK? Method Status Protocol We can do so using NAT (Network Address Translation) table of the firewall.We have 2 3945/15.0(1)M7 connected via gig interface to upstream routers (4 routers running MPLS BGP in core, dedicated for IP SLA probes) and we can ping physical interface IP just fine no delay but when ping loopback interface ping response time latency varies any where from 1 ms to 22 ms and we are looking for ways to find out if something in control plane of 3900 is causing this delay, any help is much appreciated. destination machine can directly find this out if it try to trace the incoming packets using tshark/ wireshark like tools. What this means is, we will indeed be using valid IP address of our machine to communicate with destination, but this all will happen under the hood! P.S. Having said that, in the case above to work ping -I (lookback) (destination) we can configure the firewall to transfer the requests generated by the lookback IP to be masqurade so as to change the source IP with the valid eth0 IP. as Lister maintained lookback IP is used by the device to talk to itself for self-diagnostics and trouble shooting. related discriptionĬan we actually use lookback IP to connect with other network machine? It is used mainly for diagnostics and troubleshooting, and to connect to servers running on the local machine. The loopback device is a special, virtual network interface that your computer uses to communicate with itself. We can not use lookback IP to communicate with the outside network! BUT. If you do send a packet from that ip, it will be ignored by other devices. If you have no gateway, or the gateway does not know where the network is, then the message is not sent.ġ27.0.0.1 is always on a different subnet to your network, routing devices will never route traffic from it, and your host machines will not try to send messages from it. A message will be sent to the gateway and the devices rely on the gateway to send over the message. However, if I have 192.168.0.1 ping 192.168.1.1, they will again look at the network portion and see it is different. If I try and ping 192.168.0.1 from 192.168.0.2 They will look at their subnet and identify their network portion of the ip address (192.168.0) They both see they are on the same subnet, and communicate. Lets assume your network is on the 192.168.0.0 subnet with the subnet mask of 255.255.255.0. If they are, they will talk, if not, they will attempt to use a gateway (router etc) to try and get there. When computers talk, they check to see if they are on the same subnet as the device they are talking to. If you ping 127.3.3.3 for example your device will ping itself. Local loopback uses the ip range 127.0.0.1-127.255.255.254Ī loopback device is generally assigned that entire range. I thought I would give a full answer to follow up on the comments.
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