ethernet addr for router


How many ethernet addr are there for a router? one for each port or only one for the whole router? How many ethernet addr are there for a switch?


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It all depends on HOW the router is configured, as an interface may or may not have an IP address, and in addition, the Router may have virtual interfaces that also may or may not have an address. You can have a Router that has ZERO IP address, or one that has hundreds more IP addresses than physical interfaces. It all depends on the configuration.

Again, it all depends on HOW the device is configured, for the exact same reasons.

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Unless the switch is a layer 3 switch, the switch will have only one interface. I suppose you can configure sc1 and sc2 on the old catalysts if you desire, but traditionally speaking, there is one for management.

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OP Q was about Enet addresses on a router, not a switch.

However - the lines between the 2 tend to blur these days - think of the Cat

6509 which is also the 7609 router depending on card mix, chassis label and software....

AFAIR each port on a modern router has at least 1 Ethernet adr, but may be given others due to config.

normally the ports will not have the same adr, since you might configure some things that dont like that, such as spanning tree bridging.

eg set up OSI, Decnet on the port, the extra adr is added to the original.

ie IP will use the original adr unless told otherwise, but Decnet will use the one required to define the DEC adr.

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The router will have one ethernet address for each physical interface, and one or more IP adresses (where configured) on each physical interface as well as on each virtual interface that is configured.

One single physical interface will have one ethernet address, but can have one IP address, plus secondary IP addresses, plus IP addresses on sub-interfaces......

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Arthur Brain

In your question, you asked how many ethernet addresses are there for a router. The answer is one per ethernet interface. I think what you meant to ask was how many IP addresses can be assisgned to a router.

Each interface can have at least one IP address assigned to it. Additional secondary IP addresses can be assigned beyond the primary IP address for each interface.

EXAMPLE: Cisco 7200 series router with 3 GigabitEthernet adapters interface GigabitEthernet0/1 ip address ip address secondary ip address secondary interface GigabitEthernet0/2 ip address ip address secondary interface GigabitEthernet0/3 no ip address

An ethernet switch usually only has one management IP address. Some current models of switches can allow an IP address in more than one VLAN. It is more common that there is only an IP address assigned within one VLAN known as the management VLAN. When a multilayer switch (layer 3 switch) is being discussed, then there is an opportunity to assign at least one IP address for each VLAN interface, which could be hundreds of these virtual LAN interfaces.

On a multilayer switch, you could go crazy and make each port its own subnet with the multilayer switch having a default gateway IP address for the VLAN which each port is assigned to. You could also go crazy and create 1000 VLANs on a 24 port ethernet switch and assign several IP addresses to each virtual LAN interface.

Now I ask a question back to the forum: How many IPX addresses can be assigned to a router? How many Appletalk addresses can be assigned to a router?

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