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assume want to send a packet from H1 to H3 and we have a network like this:

**H1**
A:a
|
|
N
**B1** E --- E:e **R1** F:f--- C:c**H3**
S
|
|
B:b
**H2**

How will ARP table look for these nodes in the network ? i know how ARP works and how the tables are filled but not sure how to think when there is bridges?

For example if we had a network like this:

H1 A:a --- C:c R1 D:d --- B:b H2

then then the tables would look like this:

H1 table => ip:C mac:c

R1 table => ip:A mac:a and ip:B mac:b

H2 table => ip:D mac:d

1 Answer 1

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A transparent bridge, e.g. ethernet switch, has no effect on ARP. A translating bridge, e.g. ethernet/token ring bridge, may change a MAC address between canonical and non-canonical or have some other effect, based on what it is bridging.

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  • do the bridges have tables as well ? what do they contain if they have tables? based on the network layout provided above
    – pabloBar
    Sep 14, 2016 at 2:02
  • 1
    Bridges don't have ARP tables because bridges are layer-2 devices. ARP resolves layer-3 addresses to layer-2 addresses. Bridges have MAC address tables which translate from a MAC address to a bridge interface, but a bridge gets that information from each incoming frame.
    – Ron Maupin
    Sep 14, 2016 at 2:04
  • alright, assuming we want to send a packet from H1 to H3, how will the table for H1 for example look like ? will H1´s table only contain ip:E mac:e ?
    – pabloBar
    Sep 14, 2016 at 2:09
  • Well, you said you know how ARP works, so you know that the ARP table for H1 will contain the IP and MAC addresses of its directly connected layer-3 devices (routers and hosts). It will not have the IP and MAC addresses of H3 since there is a layer-3 separation between H1 and H3.
    – Ron Maupin
    Sep 14, 2016 at 2:13
  • By ip:E mac:e i was referring to R1, So yeah H1 table will contain the direct address to R1 but will not have the address to H2... right ? please feel free to correct me if i am worng
    – pabloBar
    Sep 14, 2016 at 2:21

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