New answers tagged

1

When you have a layer-2 configuration with VLANs, each VLAN basically acts as a virtual switch. That's the point of VLANs, after all. You can think of the traffic flow as coming in through a port, getting split up (demultiplexed) into different VLAN flows, getting L2-switched independently in each VLAN, and then on the outgoing side, flows from different ...


0

The MAC address used by the spanning tree algorithm (STA) implemented in a given switch does not belong to any of its Ethernet interfaces. At least in Cisco implementations, this MAC address is known as base MAC or universal (burned-in) MAC and its purpose is to identify the switch itself, not some of its Ethernet interfaces. For this reason, this MAC ...


5

Another aspect to and expanding a bit what zac67 already gave in his answer: VLAN IDs used on tagged (sub)interfaces of routed interfaces (a.k.a. no switchport) can be completely independent from the switch's "switching" context [1]. In extenso: the VLAN tag used on the subinterface does not appear as a L2 VLAN on the switch, neither consumes nor ...


2

A subinterface is part of a physical interface, used for a single VLAN. Usually, you only have those for routed interfaces (L3) that do not take part in L2 forwarding = switching. An SVI (switch virtual interface) is a network-layer binding to the VLAN instance itself, used for routing, management, DHCP, ... - any higher-layer function apart from L2 ...


1

No. At least not directly. Domain names are a concept on the application layer. ACLs work in the network layer (simple ACLs) and in the transport layer (extended ACLs), so they can't see any names - just IP addresses and TCP/UDP port numbers. If you resolve the unwanted host names to IP addresses, then you can add those IP addresses to ACL rules and block ...


2

If you have a VLAN that is trunked between switches, then you have one layer 2 domain across all the switches. Unless you have some special cases, all devices on that VLAN would use the same gateway, which would be one SVI on only one of the switches. All devices on the VLAN will use that one gateway. One exception to this is the use of a First Hop ...


1

As a best practice, you should have an inventory of all your devices in some management scheme (or usually several ones). Even if MAC addresses are not inventoried, it should be no big problem to get them from the device lists (look up names, resolve IP addresses to MAC addresses). Then, cross compare the MAC addresses on the network with the inventory. ...


1

Put the switch port administratively down. If it is something important, somebody (or the monitoring) will complain. In the same time, have somebody go to the cabinet and identify the patch the switch port is connected to, then track down to the physical location. Personally I use a tone probe to trace cabling when there's no / outdated/ wrong labelling on ...


0

Nexus 7k support VLAN translation, so you could e.g. translate the remote VLANs 100, 200, 300 (from a trunk) to 1100, 1200, 1300 in one zone and 2100, 2200, 2300 in another. VLID translations can be tricky (esp. with RPVST+ or multiple MSTP instances), so I'd seriously recommend renumbering the VLANs. You can use translations as an interim migration scheme ...


1

I know that switch learns and stores mac addresses but my question is, how does a router know mac addresses of hosts when switch doesn't store their ip addresses? Switches have nothing to do with ARP. Only hosts with IP addresses participate in the ARP protocol. Since ARP queries are broadcast, switches forward them out all ports. Presumably, the router ...


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