Layer 3 port on switch

If I configure my switch as a router and put a port in layer 3 mode, will all vlans on the switch be able to see this ?

Hi Carl,
If all the other vlans are normal layer 2 vlans how will they see the router who will be in some other vlan or network.
You vlans will be in other subnets/networks so they need to be routed to reach the subnet/network which router belongs to.
So "ip routing" is requied and you need to have gateways for your clients in different vlans creating layer 3 interfaces for them.
HTH, if yes please rate all helpfull post.
Ankur

Similar Messages

Helper Address on a ONLY Layer 2 aware Switch

Hi,
Been scratching my head for a while now, i don't know why a switch even has the " Ip helper address" command, Dosent it need routing to acomplish this kind of a task?
I have a switch with 2 SVI's, fair enough, one for Vlan 10 and the other for Vlan 20,
Vlan 10 = 192.168.10.0/24
Vlan 20 = 192.168.20.0/24
I have a DHCP server on vlan 10, with the IP address 192.168.10.1, Now it has scopes for vlan 20 as well, i go into vlan 20 and do this:
# interface vlan 20
# ip address 192.168.20.1 255.255.255.0
#ip helper address 192.168.10.1
Now this should work right? but it dosen't !( Ive seen in Wireshark that it dosent even forward the DISCOVER Message on to SVI 10's Vlan 10 ports) ..But it does work when we configure a DEFAULT GATEWAY for the switch and the DHCP server is on a REMOTE Location where the switch does not have and interface directly connected to! what is this? its like blowing my mind! please elaborate

If this is a Layer 2 only switch then I cannot see how a helper address would work.
The SVI's you have created are going to be for management, they cannot be the Default Gateways of the Vlans IF the switch is Layer 2 only.
When your clients send out a DHCPDISCOVER message, that frame will hit the SVI address because its a 'host' on that same vlan that the client is on.
If this were a Layer 3 SVI (i.e on a Layer 3 switch) then it would forward that frame to the helper address configured. In order for the Layer 3 switch to forward the frame, it needs to do a lookup in its routing table for the destination subnet.
This is a layer 2 switch, is has no routing table so will be unable to forward the DHCPDISCOVER message to the helper address.
See here (Peters post) for an explanation of why the Layer 2 switch can act as a DHCP relay if the DHCP server is on a remote subnet:
https://supportforums.cisco.com/discussion/11385901/does-ip-helper-address-work-layer-2-switch-2950

Layer 2 multicast switching capacity

Will you tell me the "Layer 2 multicast switching capacity" of the catalyst switches(1924,2900,2950,3500,3550,3750 ,6500) and router 7600)?
Is it same as the Layer 2 unicast switching capacity?
Also, the layer 2 multicast switching is processed by hardware or software?
Thanks.

Probably not. Why? Because multicast is copied on to all ports or with IGMP and/or CGMP enabled, copied only to ports interested in such traffic. It takes more processing then a mac-address-table lookup used for unicast.
All switching occurs in hardware ASICs.

Layer 2 & 3 switch question\understanding

Hello,
I would like to have a nice explanation on a couple of things regarding layer 2 & 3 switches. The last time I asked this question it kind of went in different directions, so to avoid that I'll try and be clearer. These things below are what I do not need explanations on (followed below that I will explain what I need to understand better). What I do not need explanations on:
- I understand what vlans are
- I understand the difference between layer 2 & 3 switches
- I know what vlan trunking\tagging is
- I know what a default gateway is
- I understand that Layer 3 switches does the IP routing and layer 2 doesn't (mac addresses).
What I need to understand clearly is:
When I look at a layer 2 switch (show run) I see that the default vlan1 has no ip address and is shut down, a new vlan was created vlan10 and this vlan was given an IP address and default gateway. But the switch its self was given an IP address as well.
For ex:
interface Vlan1
no ip address
shutdown
interface Vlan10
ip address 10.10.50.2 255.255.255.0
ip helper-address 10.10.50.101
no ip route-cache
ip default-gateway 10.10.50.20
So I'm assuming the default gateway for the pc's that connect to this switch is 10.10.50.20 which is also the IP of the inside interface of the firewall.
So if that is correct then this is what I don't understand:
Why is there an IP for interface and DG address for vlan10?
Why do I read that there can only be 1 management vlan per switch? What do they specifically mean by management vlan? There has to be obviously an IP address to telnet into (10.10.40.2)? But if its used for management only why then are almost all the interfaces associated with that vlan10?
Shouldn't there be a vlan interface to access the switch and another vlan for all the computers to associate with?
So basically I need to understand better the concept of interface vlan and management vlan and ip default gateway.
Thanks!
Hello,
I would like to have a nice explanation on a couple of things regarding layer 2 & 3 switches. The last time I asked this question it kind of went in different directions, so to avoid that I'll try and be clearer. These things below are what I do not need explanations on (followed below that I will explain what I need to understand better). What I do not need explanations on:
- I understand what vlans are
- I understand the difference between layer 2 & 3 switches
- I know what vlan trunking\tagging is
- I know what a default gateway is
- I understand that Layer 3 switches does the IP routing and layer 2 doesn't (mac addresses).
What I need to understand clearly is:
When I look at a layer 2 switch (show run) I see that the default vlan1 has no ip address and is shut down, a new vlan was created vlan10 and this vlan was given an IP address and default gateway. But the switch its self was given an IP address as well.
For ex:
interface Vlan1
no ip address
shutdown
interface Vlan10
ip address 10.10.50.2 255.255.255.0
ip helper-address 10.10.50.101
no ip route-cache
ip default-gateway 10.10.50.20
So I'm assuming the default gateway for the pc's that connect to this switch is 10.10.50.20 which is also the IP of the inside interface of the firewall.
So if that is correct then this is what I don't understand:
Why is there an IP for interface and DG address for vlan10?
Why do I read that there can only be 1 management vlan per switch? What do they specifically mean by management vlan? There has to be obviously an IP address to telnet into (10.10.40.2)? But if its used for management only why then are almost all the interfaces associated with that vlan10?
Shouldn't there be a vlan interface to access the switch and another vlan for all the computers to associate with?
So basically I need to understand better the concept of interface vlan and management vlan and ip default gateway.
Thanks!

Ok but the book I'm reading says there can only be one management vlan per switch for management traffic. So all the clients in vlan10 is just a name, doesnt mean anything to them?
Yes there can be only one management vlan. But remember a L2 switch can have multiple vlans configured on it at L2 ie. in the vlan database. The restriction on a L2 switch is that you can only have one L3 vlan interface. So if you configured the management vlan to be vlan 3 for example the the switch would have 2 vlans at L2 but you would only have a L3 vlan interface for vlan 11 So -
"sh vlan brief" would show vlan 10 and vlan 11
"sh ip int brief | include Vlan" would show only one vlan interface up/up and that would be vlan 11. The only other vlan interface you would see would be for vlan 1 but it would be down with no ip address configured.
Ok, I understand all clients (switch included) use the ip address 10.10.50.2 255.255.255.0 as the default gateway (the firewall). I dont understand "If you used a different vlan to manage the switch then you wouldn't have the same default gateway as the clients. "
The default gateway is tied to IP subnet. So lets say as above you use vlan 11 for management with an IP subnet of 192.168.5.0/24.
int vlan 11
ip address 192.168.5.2 255.255.255.0
ip default-gateway 192.168.5.1 <--- the default gateway needs to be in the same subnet.
So the clients in vlan 10 attached to the switch are still using 10.10.50.2 as their default gateway but the switch is using 192.168.5.1 as it's default gateway. The device with the IP address 192.168.5.1 could be another interface on the firewall, it could be a vlan interface on a L3 switch, it could be on a router.
Now to make things simple lets say instead of the firewall both default gateways IPs are on a L3 switch.
int vlan 10
ip address 10.10.50.2 255.255.255.0
int vlan 11
ip address 192.168.5.1 255.255.255.0
the L2 switch is connnected to the L3 switch with a L2 trunk. It needs to be because you need both vlan 10 and 11 to go via the trunk.
From a PC in vlan 10 you want to connect to the switch. You telnet to the switch.
1) the PC compares it's IP and subnet mask with the IP of the switch and realises it is on a different subnet so it needs to send the packets to it's default gateway
2) the packet goes from the PC down the trunk (tagged with vlan 10) to the L3 switch
3) the L3 switch looks up the destination IP and sees it is for a 192.168.5.x address
4) the L3 switch has an interface on the 192.168.5.x subnet so it routes the packet onto that vlan and sends it back down the trunk link to the L2 switch. This time the packet is tagged with a vlan 11 tag.
5) the L2 switch receives the packet.
The return traffic is just the same but done in reverse.
Note i assumed the PC had the mac address of it's default gateway in it's arp table. I also assumed the L2 and L3 switches had all the mac address to port mappings in their respective mac address tables.
Again, please feel free to come back.
Jon

How do I configure Time Capsule to work with 8 port unmanaged switch?

This is what I want to end up with.
cable modem
Time Capsule
wireless network 8 port unmanaged switch TRENDnet TEGS80G
entertainment center(TV, xbox 360, dvd, apple tv, ect...)
I have been using the above setup with an E3000 router in place of the time capsule without any problems, and was expecting to just be able to switch out the E3000 for the time capsule and keep right on rolling. At the moment, without the switch plugged in, using the time capsule as a stand alone wireless router, everything works as intended. However, I don't want to have every device in the house pulling off of wireless. Whenever I plug my switch in I lose internet connectivity. I assume this is because both the switch and the Time Capsule are trying to direct traffic and creating a conflict. I have attempted to disable the NAT in the Airport Utility and this is what happens.
Where do I go from here, or am I heading in completely the wrong direction?

Unfortunately, you are on the wrong track, heading in the wrong direction at the moment.
We need to learn whether you have a simple modem or a modem/router.
This will determine whether the Time Capsule is to be configured in router mode to provide DHCP and NAT services for the network......or if your "modem" is already doing this.....the Time Capsule needs to be configured in Bridge Mode.
So, I suggest that you disconnect the switch from the Time Capsule for now, and power everything off except the modem, Time Capsule and the computer you are using to configure the Time Capsule, and get things working correctly first. Then, devices can be added one at a time to verify proper operation.
If this seems to make sense to you, and you want to move forward, please post back with the make and model number of your cable modem.

Ac adapter for Linksys model # EZXS88W 10/100 8-Port workgroup Switch

Please, need help finding and obtaining an AC Adapter for Linksys model3 EZXS88W 10/100 8-Port Workgroup Switch. what info do I need to narrow my search, any websites? be blessed and keep looking up!
(\O/)
/_\ ANGEL!!
Jay Paul Wilder,RN _
Be Blessed and Keep Looking Up! (\O/)
*************************************** /_\ Angel*

Try to check on this link to check the power specs of the adapter.

Catalyst 3560 24 port-PoE switch powers on but no STAT LED and console not responding

I rebooted my Catalyst 3560 24 port PoE switch and when it turned on only the STAT LED went green the other LEDs are off. I get no response from the console port using putty and the cable I used before this happened. I tested the cable on another switch and it works fine with putty. What can I do with this switch?

This unit was purchased before I came to our company. There is no support or maint contract. I'm sure the unit is several years old...we'll call the vendor and see what they'll do..not expecting much.

IOS XR Layer 2 internetworking and layer 2 local switching

I have 12410 with iox 3.6.1 and sip 501 with spa-5GE I want to configure layer 2 vpns for internetworking and layer 2 local switching. I search in the command reference and I didnt find the connect command nor internetwork ip under the PW class. can any one tell me how to configure it

Hi,
Here is an example for local switching:
RP/0/1/CPU0:router(config-if)#l2vpn
RP/0/1/CPU0:router(config-l2vpn)#xconnect group local
RP/0/1/CPU0:router(config-l2vpn-xc)#p2p ac1
RP/0/1/CPU0:router(config-l2vpn-xc-p2p)#interface gi0/3/0/0
RP/0/1/CPU0:router(config-l2vpn-xc-p2p)#interface gi0/3/0/1
RP/0/1/CPU0:router(config-l2vpn-xc-p2p)#commit
RP/0/1/CPU0:router(config-l2vpn-xc-p2p)#end
Any-2-Any connection type required 3.8
HTH
Laurent.

Sun McData Intrepid 6064 64-Port Director Switch - Lost Passwords

I inherited a Sun McData Intrepid 6064 64-Port Director Switch. It's previous netadmin is no longer available. All I can access so far is the serial port as it's default password is intact. I can't access telnet or the web interfaces due to the lost passwords. I've tried all sorts of things from different info in the web, being careful not to erase the config and licenses, but no luck so far. Has anybody had success resetting the telnet/web interface passwords on this switch, or any other McData switch? Thank you!

My SGE 2000 24 port POE switch won't boot

Hi,
I have a sge 2000 24 port POE switch that won't boot, won't communicate on console or TCP/IP, and all of the port lights are lit up green. Holding down the reset button doesn't fix the issue and there aren't any lights illuminated on the left hand side of the switch. Do I have a future doorstop?
Any ideas?

Hi David, if you're unable to console the switch, there isn't an alternative recovery method. You should check the warranty by calling the SBSC to see if you're entitled to replacement.
-Tom
Please rate helpful posts

Cisco 3750x 24 port poe switch single port is faulty.

what i can do if my cisco 3750x 24 port poe switch single port is faulty ????

Duplicate posts.
Go here: http://supportforums.cisco.com/discussion/12187366/cisco-3750x-24-port-poe-switch-failure

Cisco 3750x 24 port poe switch failure

what is the chance of cisco 3750x 24 port poe switch failure? is backup necessary for this ? please answer me in details.

If you have a Cisco switch with, at least, one faulty port you RMA the appliance.
There is nothing more detailed than that.

Linksys Cisco SRW248G4P 48-port 10/100 + 4-port Gigabit Switch Help

The switch which is a Linksys Cisco SRW248G4P 48-port 10/100 + 4-port Gigabit Switch, was configured by a contractor which was long ago run off, and the documentation left behind to log into the switch is incorrect. How can we reset this switch so we can configure to the new required settings?
I have attempted to go in through the web browser gui, and no luck logging in via factory default creditials, cannot log in using any of the common admin creditials, nor can we get in via the documented admin name and pw the contractor left.
Attempted ot go in through the console, that doesn't work right at all. Takes 15-20 min before I start even seeing user name or password boxes. Cannot type a single thing into those boxes. I have set the hyperterminal to com1, 38400, 8, none, 1, hardware. It kinda lets me see some of the log in screen, but will not let me type into the username whatsoever.
Logging via web browser I see all the login option but not a single username or pw works. Please if anyone can help, this has been an issue which is now critical.

Hi, My name is Eric Moyers. I am a Network Support Engineer in the Cisco Small Business Support Center.
The settings for connection using Hyperterminal through the Console port should be:
Bits per second: 38400
Databits: 8
Pairity: None
Stop bits: 1
Flow Control: None
When you finish configuring the HyperTerminal, the Login screen appears. The first time you open the Console Interface, use the default username admin and leave the password blank and press the Enter key. You can set a password later from the User and Password Settings screen.The Main Menu screen displays six menu choices: System Configuration Menu, Port Status, Port Configuration, PoE Configuration, Help, and Log Out.
User and Password Settings, IP Configuration, File Management, Restore System Default Settings, Reboot System and Back to Main Menu.
To restore the Switch back to the factory default settings, select Restore System Default Setting and press Enter. A confirmation message appears asking Are you sure? [Y/N]. Press the Y key to continue or the N key to cancel the action.
System Configuration Menu options: (Which is where you will need to go) consist of: System Configuration, Management Settings
After pressing Y, at this point reboot your system and it will be back to Factory Fresh.
If you have any questions or this doesn't work, please let me know. I am attachng the Admin Guide for you as well.
Eric Moyers
Cisco Support Network Engineer
1-866-606-1866

Cisco SGE2010P 48-port Gigabit Switch - Setup & Configure via Web UI?

Hello,
I'm looking to purchase a Cisco SGE2010P 48-port Gigabit Switch (POE) for a 100% Macintosh environment. Because of this, none of the machines will be able to access the switch (including initial, out of the box setup) via the console port. So, I'm wondering if anyone can confirm if this switch is configurable, out of the box, via the Web UI (which would allow a Macintosh system to set it up no problem via a web browser)? I have asked all my suppliers and talked to a Cisco Product Specialist via web chat and also tried via phone, and no one can confirm if this is possible for sure.
The reason I ask is that I was also looking at a Nortel switch and even thought it had a Web UI for management, out of the box it had to be initially set up (ie. configuring the devices IP) via the console port first, and once that was done, only then could you access the Web UI.
I'm hoping this isn't the case with the Cisco switch and that it in fact is out of the box with a default IP so it can be accessed via the Web UI (without the need to go in via the console port).
Could anyone answer this question for me!?
If it helps, this is the website for the switch I'm considering...
http://www.cisco.com/en/US/products/ps9985/index.html
Regards,
Kristin.

SGE2000 and SGE2000P must have a DHCP server to get an IP-address. You “just” have to figure out the address they have been given.SGE2010 and SGE2010P has a default IP (192.168.1.254 – 255.255.255.0)All 4 devises has a web interface. I don’t see why it shut not work with a Mac browser. The primarily reason for buying SGE switches is their ability to stack. But 24 ports (SGE2000/P) and 48 ports (SGE2010/P) switches are not able to stack with each other. They have had several years to fix the problem so it is not likely it will ever bee fixit. If you stick to eater 24 ports ore 48 ports it will work.

Uplink ports and actual sfp port in switches ( please help )

Dear all,
I am reading around to see the differences between uplink ports and normal ethernet ports. It seems to be uplink port just reverse the rx,tx pins and remove the needs of using a crossover cable.
I have done a simple representation of using the below (normal ethernet ports)
PC
SWITCH
ROUTER
RX
straight
TX
straight
RX
RX
straight
TX
straight
RX
TX
straight
RX
straight
TX
TX
straight
RX
straight
TX
I assumed that the SWITCH ethernet port pins are naturally arranged as opposite from the PC so that a straight cable can be used and the same applies to a router port.
Q1) Hence from PC to Router ethernet port, I will need a cross cable, am I right ?
============================================================
Then I chance upon this website http://duxcw.com/faq/network/uplink.htm which states "A PC can be connected to an uplink port with a crossover cable"
As per my assumption above, a router has normal ethernet ports and uplink ports (for connecting to the wan/modem), since the normal ethernet ports of a router are in the order of (RX,RX,TX,TX) as shown above, I assumed the uplink port is (TX,TX,RX,RX).
PC
ROUTER normal ethernet port
PC
ROUTER uplink port
RX
cross
RX
RX
straight
TX
RX
cross
RX
RX
straight
TX
TX
cross
TX
TX
straight
RX
TX
cross
TX
TX
straight
RX
Q2) So how can the PC connect to the Router's Uplink port using a crossover cable ? Shouldn't it be using straight cable instead if it is trying to connect to a router's uplink port ?
============================================================
Q3) Where connecting switches (switch 1 to swtich2) using uplink port, can I say that a straight cable will be connected to switch 1 uplink port on 1 end, and a normal ethernet port in switch 2 on another end ?
SWITCH#1 ethernet port
SWITCH#1 Uplink port
SWITCH#2 ethernet port
TX
RX
straight
TX
TX
RX
straight
TX
RX
TX
straight
RX
RX
TX
straight
RX
============================================================
Q4) What is the purpose of an SFP port in a switch ? is it use as an uplink port ? Where does it actually uplink/connect to ?
Q5) If i connect a switch Uplink port to another switch Uplink port, does it means that I have to use a crossover cable ? does SFP fiber come with "crossover" type too ?
============================================================
Q6) If an uplink port in a switch is use to connect to a router (can we?), do i need to use a crossover cable then ? since a normal switch ethernet port will use a straight cable to connect to a router port ? as shown below
SWITCH
ROUTER
SWITCH UPLINK
ROUTER
TX
straight
RX
RX
cross
RX
TX
straight
RX
RX
cross
RX
RX
straight
TX
TX
cross
TX
RX
straight
TX
TX
cross
TX
============================================================
Q7) Last but not least, if a design connect two switches using SFP uplink ports on both side, what would be the main purpose ? to increase the amount of ports ? Why not stack them then ?
Sorry for the lengthy post, will really appreciate if some gurus can shed some light on the above.
Thanks a million.
Regards,
Noob

Hi Noob,
On some kit like netgear hubs etc, you may find a little button or
slider switch which may be labelled MDI or MDI(X) this allows a
straight cable to be used between 2 Hubs or switches (Both DCEs).
Some Cisco switches/routers will allow you to do the same but in software
interface fastethernet 1/0/1
mdix auto
====================================
DTE devices like say your laptop PC NIC card has an MDI (Medium Dependant Interface).
Physically this wires out as ( For 10/100M):-
RJ45 PIN
1 -- TRANSMIT +ve
2 -- TRANSMIT -ve
3 -- RECEIVE +ve
6 -- RECEIVE -ve
DCE devices like hubs & swiches have MDI-X (Medium Dependant Interface - Crossedover).
Physically this wires out as ( For 10/100M):-
RJ45 PIN
1 -- RECEIVE +ve
2 -- RECEIVE -ve
3 -- TRANSMIT +ve
6 -- TRANSMIT -ve
So lets connect the device together with a STRAIGHT cable ( Function DTE to DCE)
PC/NIC = DTE = MDI                                SWITCH = DCE = MDI(X)
RJ45 PIN                                           RJ45 PIN
1 -- TRANSMIT +ve -------------------------------- 1 -- RECEIVE +ve
2 -- TRANSMIT -ve -------------------------------- 2 -- RECEIVE -ve
3 -- RECEIVE +ve --------------------------------- 3 -- TRANSMIT +ve
6 -- RECEIVE -ve --------------------------------- 6 -- TRANSMIT -ve
So we transmit from the DTE and receive on the DCE and vice versa (BINGO).
Remember Routers are regarded as DTEs
=================================
So lets connect 2 switches together with a CROSSOVER cable ( Function DCE to DCE)
UPLINK to UPLINK
SWITCH = DCE = MDI(X)                           SWITCH = DCE = MDI(X)
RJ45 PIN                                           RJ45 PIN
1 -- RECEIVE +ve -------------------------------- 3 -- TRANSMIT +ve
2 -- RECEIVE -ve --------------------------------- 6 -- TRANSMIT -ve
3 -- TRANSMIT +ve ------------------------------ 1 -- RECEIVE +ve
6 -- TRANSMIT -ve ------------------------------- 2 -- RECEIVE -ve
So we transmit from the DCE and receive on the DCE and vice versa (BINGO).
Regards
Alex

UPDATE: Deal of the Week - Cisco 3550 24 port PoE Switch

Well that didn't last long...our "Deal of the Week" this week sold out in 1 day, so we figured we better do another deal for everyone. - - - Cisco 3550 24 Port PoE Switch - $65.00 --- www.cablesandkits.com/DOW

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If you have Windows...

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