Switching Interview Questions-1

Real time switching interview question

[ashifzayn]

Noted : Layer 3 switch, all the ports in the switches are Access Ports

Scenario : Access ports communicates within the same vlan, it won't communicates from one vlan to another vlan

if it want to communicates from one vlan to another vlan, that process what we defined as Intervlan, using the device Layer 3 switch or Router

Exact scenario : Here, all the 3 PC's are connected with L3 switch, whereas it acts as Layer 2 switch.
Because when comes to Layer 3 switch, Layer 1 & Layer 2 will be active, so Layer 3 simply does not works for this scenario & it reminds quiet.
Layers 1 & 2 : switch ports, read & understand the MAC address, frame transfer (requests & replies) using access ports (within Vlan), secure check, ARP (if required).

so, there is no works for Layer 3 here & it reminds quiet.

[anilnm]

Scenario 1: ping from PC3 - If the destination Mac address of the ICMP packet is the same as the L3 switch's Gig 0/3 Mac, the L3 switch does routing.
Scenario 2: ping from PC1 to PC2 - Here the destination Mac address of the ICMP packet is different than the L3 switch's Mac address. So the switch does forwarding.

[andrejsromanovskis]

So if PC1 pings PC2 the switch is doing L2 switching due to MAC address being different. PC1 will determine if the destination is on the same network or not by checking its own IP address and subnet mask. If the destination host on the same network then MAC address will be of the destination host. If IP is on the different network then it adds MAC address of a Default gateway into the frame and switch does L3 routing.

[Nathan_Trades]

since its a layer 3 switch, i also think icmp comes to play how with the ip routing command the switch will examin the dst-ip and check if the dst-host is in the same subnet or not, if not then it will just route the packet

[srujankumar]

If routing between 2 networks needed it will perform L3 function. In case of same network L2

[RahulKumar-hhue]

When the source and destination is on the same vlan then the switches perfome L2 switching and when there is a different network and the request is for different vlan then core switch perform the routing based on the database inside the core switch if the both networks are available in the vlan database then routing will be perfome and the core connect the different network into each othe and there is IP routing command must be executed in the configuration mode because by default core switch perform L2 switching

[saurabhmishra]

Hmm ..so what i think here is : when PC1 ping to PC2 then entire path is taken from Switch ASIC, through installed FIB and adjacency tables i.e. hardware switching. But when ICMP ping is coming for SVI from PC3, it is punt to CPU for software switching hence routing.

[manishvarnika]

PC3 dont have any ip address so switch will deside based on MAc address it will act as L2 switch

[pratiktupe]

Different MAC switching and
Same MAC routing (WORKS AS GATEWAY)

[sivaraman]

More specific SVI IP is local NH in HW programming
The general subnet is receive NH / to have glean adjacency in HW programming.

So having received pkt for local IP address is observed to local RP while packet for other hosts calls for sending ARP to relearn MAC of that host for forwarding packet to them

[SIFYSE]

You can make trunk port i will be communicate all PCs

[ziaurable]

Will make L3 vlan.. interface vlan 10.. IP address