Router basic questions

[alanchia]

Hi all, there are few questions i would like to ask about routers.

1) What do u mean by static route ?
2) can 2 routers have the same IP address on their interfaces ?
3) If a link to a router is down, can the router be intelligent to know ? and to route to another way if i use static route ?
4) Can i have more than 1 identical link from a router to other equipment just for backup ? If that is so, do i have to use the same IP ?

thanks alot,
alan

 

[gconnect]

1
a static route is a means to get to the specified destination
"static" comes from the fact that the route is user-configured and the decision of that path is not decided dynamically by a routING protocol

ip route 10.1.1.0 255.255.255.0 172.18.1.2

is a static route that says "in order to get to 10.1.1.0/24 network, you have to find 172.18.1.2 first"
172.18.1.2 could be the ip address of a directly connected router interface


2 nope, if they do the routing tables will get messed up



3 Yes but only if you use "floating" static routes

ip route 10.1.1.0 255.255.255.0 172.18.1.2
ip route 10.1.1.0 255.255.255.0 172.17.1.2 100

this basically says "in order to get to 10.1.1.0/24 network, you have to find 172.18.1.2 first, BUT if that route is unreachable use 172.17.1.2" and if that 2nd gateway (172.17.1.2) is unereachable, well, you are screwed.

the 100 represents "the administrative distance". the lower the better/more preferred. the default for static routes is 1

the beauty in using dynamic routING protocols is that paths to destinations are determine by availabilty of other routers on down the line to that destination. The majority of the routers on the Internet communicate using a routING protocol called BGP. if a major router goes down, BGP in other Internet routers will recalculate their routing tables and find an alternate way around the problem device. using static routes is fine in smaller networks, but when they get to be more than say, 4 routers, it's time to start using a dynamic routING protocol.


4
if i understand you correctly that can be done using Hot Standby Routing protocol and IP Unnumberred.


Get Connected - I.T.

 

[memorable]

Hope it helps

1)static route means route that you configure yourself
For example you configure Router A to reach Router c must use router B

Dynamic route is route that is automatically configured by the router using routing protocol like RIP, IGRP , OSPF , EIGRP.

2) routers cannot have the same ip address as ip address for each router is unique unless you use NAT to make the subnet of your network to appear the same to the public but actually the ip address for each router in your network is different.

3) if you use static route the answer is no unless you specify another default static route to the router.Is like a backup route in case the router fails.

4)you have to use a different ip address as each ip address in the network is unique.

 

[alanchia]

thanks for the reply, appreciate it alot.

with these, i have further questions,

1) Can switch be used to relay the packets like what router does ?

2) If the one of the down link in the switch is down, can the switch be intelligent to use the other links ? My downlinks are connected to routers and uplink to 1 equipment.



thanks a million,
alan

 

[memorable]

for yr next question

1)switch is unable to relay packet like what router do.
Because switch is belong to layer 2 of OSI layer while router is layer three. Layer two is Datalink layer while layer three is network layer.So switch is unable to follow and select the best destination for the packets. Only router is able.

2)For your next question, i think unless you also connect the backup link to the destination using different ip addresses for each link. As for whether the switch is intelligent enough to use other link i think it is not possible unless you configure it.

 

[gconnect]

1
Yes, if it is a layer 3 switch.
a layer 3 switch will have a router module installed in them, they are a great bang for your buck in campus networks

i just installed a HP2650 switch that does layer 3 routing. you can put in up to 15 static routes in it. Other notables are Cisco's 6500 and 3550 series switches


2
if you mean 2 uplinks
Switch ======= Router
or
Switch ======= Switch

YES, if you are using Spanning Tree Protocol on the switch

STP blocks redundant paths, choosing the best path to get to one destination. If that link goes down. the STP will recalculate and choose the other link if present.

 

[alanchia]

Thanks alot for you help..