[asterisk-users] [OT] switches

Lukasz Sokol el.es.cr at gmail.com
Mon Mar 23 12:19:11 CDT 2015

On 23/03/15 16:37, thufir wrote:
> On Mon, 23 Mar 2015 10:11:54 +0000, Lukasz Sokol wrote:
>> No, ethernet switch works at lower / physical / MAC layer, NAT is
>> 'above'
>> that;
>> so as long as everything is OK with your TCP/IP settings everywhere,
>> a switch is entirely transparent to TCP/IP (or generally, when it's
>> encapsulated into MAC traffic).
> so how does a client pc find the server if there's no NAT?  by IP 
> address?? That makes no sense, to me, if the switch isn't assigning 
> addresses.
> -Thufir
+1 to what Kevin said, and

there is a protocol running on pretty much every ethernet based network,
named ARP : Address Resolution Protocol, by which ALL the clients learn ALL
the surrounding clients (including the one that is the GATEWAY) MAC/IP combinations.

Simplified, the encapsulation of ethernet packets is sort-of

| MAC Header                                  | IP Header                 | Packet
|[MAC Source address][MAC Destination Address]|[Source IP][Destination IP]|[The rest of packet]

[order and number of fields not necessarily real-life, for illustration purposes only]

now the MAC source/dest fields are added AND REMOVED as needed when the packet passes
from card to computer/router, then from computer/router to card; as the MAC fields don't make sense in 
wider area networks; 

'dumb' switches don't participate/snoop in ARP, only store a table of what card MAC address they
encountered on source MAC field of packets coming from that interconnect

manageable switches /can/ participate and filter in the ARP process if told so and have such option.


el es

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