41

I frequently use sh int | i (FastEthernet|0 packets input) or the same with GigabitEthernet, whatever kind of interfaces I want to check. sh int (which is show interfaces) gives a huge list of ste status of all interfaces The pipe symbol | can be used for filtering, but also in search expressions | i (for include) filters the output which matches the ...


39

You need to use the following command to add your VLAN 30 to an existing Dot1Q trunk on a Cisco Catalyst switch: switchport trunk allowed vlan add 30 Otherwise IOS just thinks you're trying to overwrite the existing configuration and you are left with an accidentally deleted set of allowed VLANs. You could similarly use "remove" in place of "add" to ...


34

The answer depends on whether the switch is a Layer 2 or a Layer 3 switch. That is to say, is the switch only switching and relaying traffic on to a different device for routing, or, is it doing the routing decisions itself via SVIs (switched virtual interfaces). On a layer 3 switch, the port can be found by using a few simple commands on the device. ...


28

Ultimately... DOCUMENTATION. You need to know where every patch cable goes to be 100% certain you aren't disconnecting something someone may expect to work at some point. Just because a port is currently "down" doesn't mean someone has not been using it. Also just because the counters are currently zero doesn't mean it's never been used or not going to be ...


27

Given that the Cat2960-S is a desktop/access switch, with very, very small buffers, you would likely experience a lot of output drops. A datacenter switch, such as a 4948E, would be a better choice for an iSCSI application. To understand the reasoning behind this, you have to remember that an ethernet switch is either transmitting, or not transmitting on ...


23

Dark fiber and LAG across the two links. VPLS won't work on 4500. Disable STP on the DCI link (and make sure nobody ever reconnects the cables the wrong way) or use MST with each DC as a region (you don't want STP events in one DC to spill over into the other). In theory you could use Metro Ethernet services, but if they don't pass LACP and STP ...


19

172259: May 6 14:43:06: %BGP-3-NOTIFICATION: sent to neighbor xxx.xxx.12.34 4/0 (hold time expired) 0 bytes That generally means the other side of the connection did not respond to any keepalives within the hold timer (default 180 seconds). There are a variety of issues that could have caused this. Usually its a layer3 reachability issue. If it happens ...


19

"Bus" is connection to 16Gbit/s bus that is common to legacy 6500 architecture. Crossbar and dCEF mean the connection from the LC (line card) is using switch fabric (separate SFM module for Sup2, integrated switch fabric chip on Sup720 and Sup2T). Crossbar means the connection is from the line card that doesn't have distributed processing capabilities (no ...


19

Is it correct in assuming that ASICs for router or switch interfaces will outperform the use of an x86 CPU for all packet processing which will greatly suffer from CPU interrupts? It's hard to say specifically whether interrupts are a limitation, since we aren't naming specific CPU, operating system or router models in this part of your question. Overall, ...


16

Is it possible to allot IP address based on MAC address on CISCO CE 500 No you need a real Cisco IOS switch for DHCP server functionality with Maunal Bindings; the Catalyst Express series switches do not run IOS


15

From the configuration guide: Frames sizes that can be received by the switch CPU are limited to 1998 bytes, no matter what value was entered with the system mtu or system mtu jumbo commands. Although frames that are forwarded or routed are typically not received by the CPU, in some cases packets are sent to the CPU, such as traffic sent to control ...


15

The Cisco 2960-X is an IOS platform. According the to the datasheet it ships with LAN Lite, LAN Base, or IP Lite(all IOS variants) depending on the hardware you select. You may want to consult the documents linked below to determine what feature(s) you require, as the lite models cannot be upgraded to the comparable base IOS version. 2960-X Data Sheet 2960 ...


14

http://packetlife.net/blog/2012/jan/16/catalyst-2960s-iscsi-optimization/ I followed Jeremy Stretch's post here a while back, moving our iSCSI SAN off a production switch onto a dedicated 3750G (stack of 2). While I can't speak specifically to the 2960S, the tweaks offered in that post seem to be doing well on the 3750G's. I've got a handful of ...


14

Unless someone is clearing counters you should never see any odometer-type counters (those that increment based on a packet action) decrease, they should always increase. That part sounds like a bug. As far as what causes output drops in particular, there are so many different causes that it's very difficult to pinpoint it exactly. Sometimes there is ...


14

The switch will fully load the incoming frames of data, from the two sending systems, into its buffer(s). I'm not sure how it determines which frame would be first in the queue for subsequent forwarding; but it's probably based on initial receive time of the beginning of the frame. Then the switch works through the transmit buffer queue sending the frames ...


13

Try this: show platform hardware interface ten1/1/31 statistics That should show you input bytes by CoS. The 4500 is a very different beast than the 3560/3750 for qos config and monitoring. Some other useful verification commands are: show platform hardware qos interface foo X/Y shows queue lengths and flow counts show interface foo X/Y counter detail ...


13

Firstly, you need to get the MAC address, so get into a machine on the same VLAN and look at its neighbour table - Windows is netsh int ipv4 show neigh, Linux: ip nei Cisco: show ip arp x.x.x.x. Once you have that... If this is a discovery job on a layer 2 switch, do show mac address-table | i 0011.2233.4455 - replacing the mac address bytes as appropriate. ...


13

FWIW I've had experience with 3750's (3750G, and then later 3750E/3560E) at scale in a TOR setup; initially with L2 port-channels/GLBP (variants of 2x1G and 2x2G and the rare 2x4G for db racks) and then with L3 to the TOR (went with this for 3750E/3560E and 10G to the core). I'm talking thousands of them. We only saw issues with buffers for the most ...


13

SSO is preferred due to shorter switchover if supervisor fails. From Cisco: With supervisor engine redundancy enabled, if the active supervisor engine fails or if a manual switchover is performed, the standby supervisor engine becomes the "new" active supervisor engine. The standby supervisor engine has been automatically initialized with the startup ...


13

I don't have SUP7 to test, but it works on SUP6 and SUP32, I would presume SUP7 retains this functionality. I've tested between JNPR M320 <-> SUP32, and 'vlan mapping JNPR SUP32' works just fine. There is no need for QinQ, what the QinQ option does is it adds top tag to one particularly tag. So switchport vlan mapping 1042 dot1q-tunnel 42 would map ...


12

I also like sh int | inc line protocol is|Last input which outputs FastEthernet0/29 is down, line protocol is down (notconnect) Last input never, output never, output hang never FastEthernet0/30 is up, line protocol is up (connected) Last input never, output 00:00:07, output hang never FastEthernet0/46 is down, line protocol is down (notconnect) ...


12

I think that you have another switch or hub connected to port 24 of your 2960, and there are 4 hosts connected to that switch/hub.


11

My knee jerk reaction to this would be to say "don't do it." Mainly because these switches would not support data center bridging. FCoE is not like iSCSI. FC is a bus and assumes it is lossless. Ethernet, as you know, is lossy. DCB allows Ethernet to act lossless and transport FCoE frames.


11

I like @Stefan's answer but with this command line "sh int | i (Ethernet| 0 packets input)" which now grabs all Ethernet interface types and filters out non-zero numbers that happen to end in zero. He mentioned that some fine tuning might be possible so this is just one example. Another option is... sh int counters | i (Port|_0 0 ...


11

I would scrape the output (or grab it with SNMP, even better) and use standard UNIX tools to parse it. Here's an easy example: Here, I saved a partial output from 'show int counters' (just for demo purposes) to a file called "counters". [mkantows@ochofu049]$ cat counters Port InOctets InUcastPkts InMcastPkts InBcastPkts Gi1/0/1 ...


11

4500 line cards are hot swapable, so the answer to the first three questions is yes (assuming a 45xxR chassis). A couple of caveats, for question 2, the supervisor has to meet the requirements for redundany. For instance, you would not be able to insert a Sup7 in a chassis with a SupIV. Additional configuration may be required as well to enable the ...


11

3750 does have some internally priority on what it prefers to punt when congested, but it's not configurable. So you should rely on common best practices, that is on all your network edges you should have iACL (infrastructure ACL). In iACL you'd allow UDP highports, ICMP to infrastructure network addresses and drop rest. This way ping and traceroute work, ...


11

You can use short range SFP optics for this. The Cisco part number is GLC-SX-MM, and the cost is about $75-$100 each (you'll need two). The person installing your fiber should use 50uM multimode fiber (62.5uM is also useable, but you're getting close to the maximum range) with LC type connectors.


11

tl;dr The switch management cannot send anything to a different layer-3 network without a default gateway. Telnet is a bidirectional protocol, and the switch, without the default gateway, would be unable to respond to the host which is attempting to establish the Telnet session. Long explanation: The default gateway on a switch has the same function as ...


11

You really, really do not want to disable STP where you connect switches to other switches. That is the entire purpose of STP. If you disable STP, and there is a problem, it will really be too late because your entire network could crash when you notice it, and recovering from a broadcast storm is no fun at all. By the way, portfast doesn't actually disable ...


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