I am wondering if anyone can assist me with this router problem. Our facility uses NetMRI for monitoring our network equipment and LAN health. Ever since we switch from using our 4506 switch as the uplink to the WAN to using a port on our Gig blade as the uplink to our 2821 router, we have seen increasing amount of broadcasts on the router interface. Here is how we are connected:
The output of the switch interface doesn't show any errors, however the input of the router has a high error count. NetMRI has reported high interface errors, Cisco buffer misses high and high CPU utilization. I need some help in determining if the router has the real issue or the switch is causing the issue. I have included the results of the show interface for both the switch and router.
I hope someone can assist me in determining the route of this problem. THANK YOU
2821-Router #show interface gi0/0
GigabitEthernet0/0 is up, line protocol is up
Hardware is MV96340 Ethernet, address is 001f.cae2.ca60 (bia 001f.cae2.ca60)
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 4/255
Encapsulation 802.1Q Virtual LAN, Vlan ID1., loopback not set
Keepalive set (10 sec)
Full-duplex, 1000Mb/s, media type is T
output flow-control is XON, input flow-control is XON
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters 19:34:01
Input queue: 0/75/41555/0 (size/max/drops/flushes); Total output drops: 0
A cisco 2821 can support approx 87Mbps of CEF traffic so even though it has a gig interface it cannot support anywhere near that. A 4500 switch on the other hand, depending on the supervisor/module/chassis combination could get a lot closer to the 1Gbps mark. So what is the WAN circuit speed and how much traffic do you normally send and receive on the WAN ?
Thanks for the reply Jon. The backbone is currently 1 Gig. The incoming port on the 2821 is a confusion of 5 VLANs all of which are set for 1Gbps. As you could see, the output from the 4506 shows nothing excessive or any errors, but the input on the 2821 has numerous errors and buffer misses. Here is the information on the 4506.
Sorry, i thought the issue was with the WAN port on the 2800 not the port connecting to the 4500.
So you have a gi0/0 port running 802.1q encapsulation by the looks of it connecting to the 4500. Which means the 4500 port is configured as a trunk ? If so have you cleared all the vlans off that trunk except for the 5 vlans that the 2800 is routing for ?
But in answer to general question, if the 4500 gig link is putting out more than approx 100Mbps then yes you will see drops on the 2800 router. But it depends on how much WAN speed you have so what is the speed of the WAN link ?
I ask because if the WAN link was 200Mbps for example and the 4500 was transmitting about 200Mbps to the 2800 then the router is now a bottlebeck and you will see drops. So you would need to think about a new router with greater througput. However if the WAN link was 50Mbps and the 4500 was transmitting 200Mbps then you may be able to use QOS to limit traffic coming from 4500 to 2800 and to prioritise traffic on the 2800.
Thanks for providing me some education here. To respond to your first thought... I believe you are correct to say that the router is the bottle neck. I cannot give you the actual throughput from the switch interface to the router interface and then out on the WAN. Unless the 4506 or the 2821 can provide some measurement, I will not know. The only things I do know are:
Link from switch to router are gig links.
The interface coming out of the switch is trunked and is being used by 6 VLANs for data and 1 management VLAN.
The interface for the router is routing has all the VLANs routed through that interface.
The connection between the links are done via a RJ45 UTP cable.
The switch also has the group of ports 1 - 4 all connected with 3 ports using 1GB and 1 using 100Mb connections. The two Gig connections domain controllers and DNS server.
QOS seems like the way to go. but I had a thought a couple of days ago to utilize the other interface on the 2821 to route some of the VLAN traffic. Would that too be a viable solution in conjunction with QOS? I do know one of the VLANs are creating the most traffic and broadcast noise.
Your input has been very valuable to me as a networking rookie. Thank you very much for your assistance.
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