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Home > Archive > alt.certification.cisco > February 2004 > [CCNA] IP address group routing....
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[CCNA] IP address group routing....
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| I am studing for my CCNA and I have a question....
If the IP address is not in the router group how does the router know
which router to send it to? does it send it to one that is arbitrary
on it's list or what?
:huh:
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| smrkdown 2004-02-22, 8:13 pm |
| If I understand your question correctly, it would use default routing using the gateway of last resort which can be assigned with the following command where xxxx.xxxx.xxxx.xxxx is the address of the next hop router:
Router(config)#ip route 0.0.0.0 0.0.0.0 xxxx.xxxx.xxxx.xxxx
Packets destined for networks not found in the local routing table will be sent to the gateway of last resort. This is equivalent to setting the default gateway on a PC.
If the router is not a stub router and there is no entry for a gateway of last resort and there is also no entry for that network in the routing table, you will receive a destination unreachable. | |
| The Flyer 2004-02-22, 10:25 pm |
| If it is a stub router, or default router is set due to any other
reason, the packet will be forwarded to that particular route. If no
default router has been set, the packet will be discarded, as it is
the inherent nature of routers to discourage broadcasts.
Thats all what I know; if somebody could provide a better explanation,
he/she is most welcome.
The Flyer.
ciscofaq@hamawy.com (Goha) wrote in message news:<16df6ca5.0402221123.4ca9dc1d@posting.google.com>...
> I am studing for my CCNA and I have a question....
>
> If the IP address is not in the router group how does the router know
> which router to send it to? does it send it to one that is arbitrary
> on it's list or what?
>
> :huh:
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| am1one4u@yahoo.com (The Flyer) wrote in message news:<7e6d9555.0402221835.16bd418@posting.google.com>...[color=blue]
> If it is a stub router, or default router is set due to any other
> reason, the packet will be forwarded to that particular route. If no
> default router has been set, the packet will be discarded, as it is
> the inherent nature of routers to discourage broadcasts.
>
> Thats all what I know; if somebody could provide a better explanation,
> he/she is most welcome.
>
> The Flyer.
>
> ciscofaq@hamawy.com (Goha) wrote in message news:<16df6ca5.0402221123.4ca9dc1d@posting.google.com>...
this is where i am confused.
example...
there is network a, network b, network c, network d....
network a sees only networks b and c in its routing table.
how does it know how to route the packet to network d?
does it throw the packet out into the internet hoping that it will get
to the correct place or what?
after it finds the place (if it does) does it add it to the router
table as a new entry?
This concept is totally killing me here...
please help me.........
Thanks a lot.....................
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| Secret Squirrel 2004-02-23, 1:25 pm |
| ciscofaq@hamawy.com (Goha) wrote in
news:16df6ca5.0402230809.258e0679@posting.google.com:
> am1one4u@yahoo.com (The Flyer) wrote in message
> news:<7e6d9555.0402221835.16bd418@posting.google.com>...
>
> this is where i am confused.
>
> example...
>
> there is network a, network b, network c, network d....
> network a sees only networks b and c in its routing table.
>
> how does it know how to route the packet to network d?
>
> does it throw the packet out into the internet hoping that it will get
> to the correct place or what?
>
No. Either there is a route in the table or not. If there is a route in
the table the packet gets routed. If there is no route in the table but
there is a gateway of last resort defined then all packets with unknown
destinations will be routed here. If there is no gateway of last resort
(default gateway) defined, the packet is discarded
> after it finds the place (if it does) does it add it to the router
> table as a new entry?
No, routing tables are updated by the routing protocols. The network will
converge when it is brought up. Changes to the routing table will happen
periodically as routes become available or unavailable but again these
changes are made by the routing protocols.
>
> This concept is totally killing me here...
>
> please help me.........
>
> Thanks a lot.....................
>
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