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VLAN protection on a PC with 2 NICs

Hello,
I have a pc (say PcA) with 2 NICs;
each NIC is associated with a VLAN (say VLAN 1, e.g. 172.50.x.x and VLAN2,192.168.101.x );
another pc (say PcB) has 1 NIC, in VLAN2

Pc A=====(VLAN1 / VLAN2)====SWITCH----------------(VLAN2)------PcB
|__ROUTER(for trunking)

A user would typically enter the network thru the SWITCH which is connected with a firewall then a router (not shown in the above picture) and then the Internet.

A user coming from the Internet can access PcA thru VLAN1.

Questions:

1) Once a user has access to PcA (on VLAN1), how should PcA exactly be configured to allow him to reach PcB (I think i should add some command like: route add 192.168.101.0 255.255.255.0 <what gateway ??> ), is this correct ?

2) With this configuration, is there any way to prevent PcA from reaching PcB ?

3) Is there anyway to allow such an access as "Read-only", I don't think so actually...

Thanks a lot in advance

syn_ack_fin

1) Nothing. If PcA has a NIC on each VLAN then there will aready be routes created for each segment it is attached to. If PcA was ONLY attached to VLAN1, then he would need the gateway set to whatever router is routing IP traffic across VLAN's in your network.
2) If it has a physical attachment to each VLAN then the answer is no. If the system is only on VLAN1 and is routing to VLAN2 then you can use ACL's.
3) No. Read-Only would be setup on the OS level, not the switch.

Good Luck

ASKER CERTIFIED SOLUTION

JFrederick29

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minicuc

ASKER

So basically it does not matter what VLAN I am starting from, once I have connectivity with PcA I can reach PcB (if no other config on switch or other is done), right?

Access-list...you mean MAC address filtering, right ?

Where would it be better to place the Sw firewall, on PcB ?

Thanks

JFrederick29

As long as they are in the same VLAN, you can communicate with one another.

No, I mean filtering based on IP address but you would need a layer 3 switch to do that. I suppose you could use MAC address filtering...

Sure, install it on PCB and have it drop all packets from PCA but allow all others.

minicuc

ASKER

Sorry Jfrederick, I still am not clear about the first point:

if I reach PcA from another Pc which belongs to VLAN1, would I be able to communicate with PcB ?

JFrederick29

No, if you want other PC's to be able to reach PCB, through PCA, PCA would need to be routing between the two subnets (VLAN's).

Since you have a router trunking, I assume it is providing routing between VLAN1 and VLAN2, PC's on VLAN1 will route through the router to reach PC's on VLAN2.

minicuc

ASKER

You are right, in case the router were not providing trunking and I still had 2 NIcs on different subnets, the routing could be done by PCA itself (commands: route add etc...and which gateway ?).
thx

JFrederick29

Actually, depending on the operating system, you need to enable routing, either using RRAS in Server version or using a registry edit to enable routing in XP or 2000 professional.

http://www.wown.com/j_helmig/w2kprout.htm