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Cant ping next hop IP using switch as default gateway

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  • 1.  Cant ping next hop IP using switch as default gateway

    Posted Dec 16, 2014 01:55 AM

    I have an S2500-48P with 3 VLANS on it. VLAN 1(IP 192.168.1.254/24), VLAN 2(IP 192.168.3.254/23), VLAN 3(IP 192.168.5.254/23). I am using the switch as the default gateway for all the clients Traffic is then NAT'ed on a cisco router with LAN IP 192.168.1.252. I se the default gateway of the switch to 192.168.1.252. When I do a show ip route I see the following

     

    0.0.0.0 0.0.0.0 via 192.168.1.252

    192.168.1.0/24 connected on VLAN 1

    192.168.1.254/32 connected on VLAN 1

    192.168.2.0/23 connected on VLAN 2

    192.168.3.254/32 connected on VLAN 2

    192.168.4.0/23 connected on VLAN 3

    192.168.5.254/32 connected on VLAN 3

     

    Client 1 (IP 192.168.1.251 subnet 255.255.255.0 DG 192.168.1.254)

    Client 2 (IP 192.168.3.251 subnet 255.255.254.0 DG 192.168.3.254)

    Client 3 (IP 192.168.5.251 subnet 255.255.254.0 DG 192.168.5.254)

     

    Client 1 can pin the next hop (192.168.1.252) and can ping client 2 and 3.

    Client 2 and 3 can ping each other and can ping VLAN 1 switch IP (192.168.1.254) but cant ping next hop (192.168.1.252). 



  • 2.  RE: Cant ping next hop IP using switch as default gateway

    Posted Dec 16, 2014 04:28 AM

    Hi Friend,

     

    Can you share some more information ? such as,

     

    1. L3 config of VLANs , "show ip interface brief"

    2. NAT config. "show interface vlan <id>"

    3. Routing table of the cisco router, "show ip route"

     

    Please comeback with the above info, I will surely help you to fix the issue.

     

     



  • 3.  RE: Cant ping next hop IP using switch as default gateway

    Posted Dec 16, 2014 05:40 AM

    I have had to add a few more vlans but the essentials are the same. Herewith the following 

     

    1) Show IP interface brief

    Flags: S - Secondary IP address

    Probe: U - Up, D - Down, U/O - Up & Own IP, N/A - Not Applicable

    Interface                   IP Address / IP Netmask        Admin   Protocol Probe  Flags

    vlan 1                   192.168.1.254 / 255.255.254.0     Up      Up       N/A           

    vlan 10                 192.168.19.254 / 255.255.254.0     Up      Up       N/A           

    vlan 12                 192.168.23.254 / 255.255.254.0     Up      Up       N/A           

    vlan 13                 192.168.25.254 / 255.255.254.0     Up      Up       N/A           

    vlan 14                 192.168.27.254 / 255.255.254.0     Up      Up       N/A           

    vlan 2                   192.168.3.254 / 255.255.254.0     Up      Up       N/A           

    vlan 20                 192.168.39.254 / 255.255.254.0     Up      Up       N/A           

    vlan 3                   192.168.5.254 / 255.255.254.0     Up      Up       N/A           

    vlan 300                    unassigned / unassigned        Up      Up       N/A 

    vlan 5                   192.168.9.254 / 255.255.254.0     Up      Up       N/A           

    vlan 7                  192.168.13.254 / 255.255.254.0     Up      Up       N/A           

    vlan 8                  192.168.15.254 / 255.255.254.0     Up      Up       N/A           

    vlan 9                  192.168.17.254 / 255.255.254.0     Up      Up       N/A           

    mgmt                        unassigned / unassigned        Up      Down     N/A 

     

    2 ) I am not doing any NAT on the switch.

     

    3) Cisco config is as below

    interface GigabitEthernet0/0

    description To-LAN-network

    ip address 192.168.1.252 255.255.0.0

    ip nat inside

    ip virtual-reassembly in

    load-interval 30

    duplex auto

    speed auto

    no cdp enable

    !

    interface GigabitEthernet0/1

    description To-ISP-router

    ip address 41.xxx.xx.xx 255.255.255.248

    ip nat outside

    ip virtual-reassembly in

    load-interval 30

    duplex auto

    speed auto

    no cdp enable

    !

    ip forward-protocol nd

    !

    no ip http server

    no ip http secure-server

    !

    ip nat inside source list 1 interface GigabitEthernet0/1 overload

    ip nat inside source static tcp 192.168.2.253 80 41.xxx.xx.xx 80 extendable

    ip nat inside source static tcp 192.168.2.236 80 41.xxx.xx.xx 1236 extendable

    ip nat inside source static tcp 192.168.2.237 80 41.xxx.xx.xx 1237 extendable

    ip nat inside source static tcp 192.168.2.238 80 41.xxx.xx.xx 1238 extendable

    ip nat inside source static tcp 192.168.2.239 80 41.xxx.xx.xx 1239 extendable

    ip nat inside source static tcp 192.168.2.240 80 41.xxx.xx.xx 1240 extendable

    ip nat inside source static tcp 192.168.2.241 80 41.xxx.xx.xx 1241 extendable

    ip nat inside source static tcp 192.168.2.8 22 41.xxx.xx.xx 2222 extendable

    ip nat inside source static tcp 192.168.2.253 8080 41.xxx.xx.xx 8080 extendable

    ip nat inside source static tcp 192.168.1.250 8181 41.xxx.xx.xx 8181 extendable

    ip nat inside source static tcp 192.168.1.250 22 41.xxx.xx.xx 8282 extendable

    ip nat inside source static tcp 192.168.2.8 80 41.xxx.xx.xx 8888 extendable

    ip nat inside source static tcp 192.168.2.8 10000 41.xxx.xx.xx 10000 extendable

    ip route 0.0.0.0 0.0.0.0 41.190.46.49

    !

    access-list 1 permit 192.168.0.0 0.0.255.255

     



  • 4.  RE: Cant ping next hop IP using switch as default gateway

    Posted Dec 16, 2014 07:38 AM

    HI,

     

    As per the information given, Routing table and the VLAN interface info are not matching.

    as per the VLAN interface :

     

    VLAN 1 : 192.168.1.0 /23

    VLAN 2 : 192.168.3.0 /23

    VLAN 3 : 192.168.5.0 /23

     

    rt2.JPG

     

    As per the routing table of the switch :

     

    VLAN 1 : 192.168.1.0 /24

    VLAN 2 : 192.168.2.0 /23

    VLAN 3 : 192.168.4.0 /23

     

    RT1.JPG

     

    Here my point is, why VLAN 1 subnet is populated as /24  in the routing table ? and summarised routes of VLAN 2 and 3 are showing different ?

     

    if you made some changes after showing the routing table please share the current routing table

     

    Please feel free to come back on this



  • 5.  RE: Cant ping next hop IP using switch as default gateway

    Posted Dec 24, 2014 04:55 AM

    Thanks for all the help. Turns out that the NAT router which is controller by the ISP didnt have the correct routes on it. SO got them to add the routes for the rest of the subnets and we are all up and running.

     

    Thanks again for the help