12
votes
Accepted
Should I disable STP on my access ports?
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 ...
- 98.4k
11
votes
Accepted
Meaning of the ip default-gateway L2 switch
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 ...
- 98.4k
9
votes
Accepted
Locked myself out of my Cisco switch
If you didn't save the configuration, you could just restart the switch, but you will need physical access to the switch. You may be able to get someone at the site to restart the switch for you. ...
- 98.4k
8
votes
Accepted
When and where to use Spanning-Tree (Portfast)
Spanning tree only runs between switches, never to standard end hosts.
Bear in mind that, under normal circumstances, a port supporting spanning tree will (when it first comes up) run through a ...
- 6,104
8
votes
Accepted
2960X Management VLAN
You can disregard the dedicated management interface and simply assign an IP address to the VLAN 500 interface on the switch and use this IP for management purpose, with appropriate access lists.
FE0 ...
- 19.4k
8
votes
Accepted
Switching interface VLAN ID Mid-Production
I was wondering if there was a way to switch out the VLAN ID from
VLAN1 to VLAN10 without impacting the connectivity of the end users?
No.
First, you must remove the addressing from VLAN 1 before ...
- 98.4k
7
votes
Overlapping IP addresses in CISCO 3650
Your subnet mask is 255.255.0.0 (also written as /16). That means the first 16 bits of the IP address define the network, and the last 16 bits are the host address. With that mask, there are 65534 ...
- 66.9k
7
votes
Accepted
Fix our Cisco switch overwhelmed by console logging
I have a setup with dual redundant Cisco catalyst 4506-E using the WS-X45-SUP8L-E supervisor engine and two 48-port switches below it.
My task is to access and modify the switch configuration.
...
- 29.9k
7
votes
How to Change the Date on Cisco Catalyst 3750x Switch
The order of operations is important because setting the time first will result in the time being incorrect after issuing the zone commands, so what you need to do is:
First, you set the regular time ...
- 4,690
7
votes
How do I know the switch is layer 2 or layer 3?
In addition to @Zac67 answer, in the Catalyst product line, layer 3 capabilities are often unlocked by licenses.
So a given switch can be layer 3 capable but, depending on the installed license, may ...
- 19.4k
6
votes
Cabling standard for Layer-3 switch
I want to know the appropriate cable type between:
Layer-2 and Layer-3 switch
Layer-3 switch and router
Is it cross-over or straight through?
You need to make the distinction ...
- 1,636
6
votes
Accepted
Will a Wi-Fi Access point affect maximum addresses configured via port-security
That depends on how the access point is configured. If it's configured as a router you'll only see one address of the access point itself, but if it's configured as a bridge between the wireless and ...
- 17k
6
votes
Accepted
Basic Catalyst 3560 Egress Shaping
And now the real question:
To shape all unclassified egress traffic to fit into 50 Mbps, can I just enter
srr-queue bandwidth shape 0 2 0 0 on the interface in question and be done?
It ...
- 1,135
6
votes
What should a device do with an Ethernet frame larger than its MTU?
The ethernet standard (IEEE 802.3) calls the large frames damaged because the bits where the FCS is supposed to be don't match the CRC of the bits coming before them. What you see the Cisco switch do ...
- 98.4k
6
votes
Accepted
Port channel to two different switches
I understand that this is an incorrect configuration, but what was blocking traffic to the new switch? Is this part of the port channel or spanning tree or something else?
Nothing was actually "...
- 27.2k
6
votes
Factory Reset Cisco 3560: Stuck in loop
Sounds like a nice job of a botched content ot the boot variable - possibly the config file variable. The switch: prompt you see there is called the ROMMON prompt. ROMMON is a bit like the BIOS of a ...
- 8,739
6
votes
Accepted
Cisco 3750G - SSH Diffie Hellman Group 1 SHA1 Error
Your SSH client is saying "we can't agree on the cipher: server wants X but I'm configured not to speak X". This is a completely general SSH problem, not specifically related to this model of switch, ...
- 16.1k
6
votes
Accepted
QoS policy definition - Cisco guidelines vs reality
If you are using eight classes, then you are probably overthinking it. You want most traffic to be in the default class, protect real-time traffic with a priority class and policing, make sure that ...
- 98.4k
6
votes
Accepted
cisco switchport trunk native vlan
The problem is not the traffic from the server to the switch, but the return traffic, from the switch to the server.
Since the VLAN is native, the switch will sent the traffic for this VLAN untagged, ...
- 19.4k
6
votes
Accepted
PortFast For Some Networks But Not Others
We don't know the configuration of your servers and PCs - which is off topic here.
Portfast allows the switch ports to transition their spanning-tree mode to forwarding immediately. Without Portfast, ...
- 66.9k
5
votes
Accepted
KEMP load balancers using UCARP (VRRP) - multicast MAC address not being picked up
I was able to resolve the issue. On the Kemp (with HA pair) you have the option of using a "Virtual MAC Address". If this box isn't checked, then the MAC of a load balancer VIP is that of the physical ...
- 86
5
votes
Cabling standard for Layer-3 switch
I don't know what hardware you're specifically talking about here, but modern switches and routers support auto-MDIX which essentially eliminates the need for crossover cables.
Since you used a Cisco ...
- 2,102
5
votes
Cisco 3750 switch stack with different IOS images
You should really set the IOS version to be the same before adding a switch to the stack. Basically, the switches need to have the same stack protocol version, and only switches with the same IOS ...
- 98.4k
5
votes
Accepted
How did I break (half of) my network?
It sounds like you created a broadcast storm, and the only way to stop it is to power down the switches. Having lived through this several times, we have adopted some best practices recommended by ...
- 98.4k
5
votes
Accepted
Lab: I need to determine information about a device on a specific port of a Cisco multilayer switch
ARP is a protocol to resolve a layer-3 address to a layer-2 address. If there is no layer-3 address assigned to the device, then ARP cannot help you.
Apparently, the device is sending frames because ...
- 98.4k
5
votes
Accepted
Can you SSH to a Cisco switch without a Username
You need some sort of credentials for SSH to work. You can either set it up using passwords like normally, or you can use a certificate to authenticate.
Here's a discussion that might be helpful: ...
- 2,249
5
votes
Accepted
Can a broadcast storm do physical damage to computers and networking hardware?
I don't think this is possible. A broadcast storm from a bridge loop will effectively bring down much/all of your network (depending on bandwidth) but doing some permanent damage to the hardware is ...
- 81.6k
Only top scored, non community-wiki answers of a minimum length are eligible