Question on ingress and egress

hitmenhitmen Banned Posts: 133
If I ping a remote end, the packet has to return. In that case, will the ingress and egress interface change?

If I apply a policy to one interface, will the policy be applied when the packet goes in or leaves?

For example, if I place encapsulation dot1q on an interface, will a packet be encapsulated twice if it goes through this interface to the next hop and returns from the next hop to the original interface?icon_cry.gif

Comments

  • NetworkVeteranNetworkVeteran Member Posts: 2,338 ■■■■■■■■□□
    hitmen wrote: »
    If I ping a remote end, the packet has to return. In that case, will the ingress and egress interface change?
    From a routing perspective, the forwarding of a data packet typically won't result in any network changes.
    If I apply a policy to one interface, will the policy be applied when the packet goes in or leaves?
    That depends on whether you apply the policy to outgoing/egress traffic or incoming/ingress traffic.
    For example, if I place encapsulation dot1q on an interface, will a packet be encapsulated twice if it goes through this interface to the next hop and returns from the next hop to the original interface?icon_cry.gif
    From a routing perspective, the L2 encapsulation you choose is only inserted/added to outgoing packets. The next-hop strips away whatever you add. E.g., you might add a PPP header to a packet before sending it over a serial link, but that next router will strip that completely away before sending the packet over an Ethernet link.

    It's very important in networking (and to earn your CCENT) to understand the different OSI layers.
  • Dieg0MDieg0M Member Posts: 861
    hitmen wrote: »
    If I ping a remote end, the packet has to return. In that case, will the ingress and egress interface change?

    If you have asymmetric routing in a redundant network, your icmp packet will sometimes have a different ingress and egress interface. You can check this by specifying the ping extended command and turning on the record option for a hop by hop interface mapping of the icmp packet.
    hitmen wrote: »
    If I apply a policy to one interface, will the policy be applied when the packet goes in or leaves?

    I'm assuming you are talking about PBR and the policy is applied on ingress interfaces.
    Follow my CCDE journey at www.routingnull0.com
  • hitmenhitmen Banned Posts: 133
    From a routing perspective, the forwarding of a data packet typically won't result in any network changes.


    That depends on whether you apply the policy to outgoing/egress traffic or incoming/ingress traffic.


    From a routing perspective, the L2 encapsulation you choose is only inserted/added to outgoing packets. The next-hop strips away whatever you add. E.g., you might add a PPP header to a packet before sending it over a serial link, but that next router will strip that completely away before sending the packet over an Ethernet link.

    It's very important in networking (and to earn your CCENT) to understand the different OSI layers.

    Oh. I forgot something very fundamental. L3 strips away the vlan layers and in L2 the vlan will just keep passing traffic and loopback mechanisms have to be prevented.

    There is no ping in my big L2 switch network so the DATA FRAME wont come back. silly me!
  • DCDDCD Member Posts: 453 ■■■□□□□□□□
    It's very important in networking (and to earn your CCENT) to understand the different OSI layers.

    He said he's a CCNA.
  • hitmenhitmen Banned Posts: 133
    Give me a break. I am testing switches from zte, juniper and cisco and somehow I have to get them to work together. Unfortunately they are L2 and I cant get them to do ping or traceroute. So I have to see the mac address and vlan. icon_wink.gif
  • CyanicCyanic Member Posts: 289
    @hitman - after reading through some of your other posts I don't believe you deserve a break. It sounds to me that you are in a job that is well over your head. I think it has been mentioned to you that you should pick up and study a Network+/CCNA book so you can get a better understanding of your job.
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