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Connecting SG300-10 to C1921 router

Hi everybody,

I have a newbie question (I might bein over my head, please be gentle)

My ISP has built a MPLS network for me and all has been simple so far connecting everything together. They have supplied me with C1921 routers and configured the default gateways so I could just program network cards etc to point at the internet. This has all gone well. The final challenge I face is to setup my head office. To me this is a slightly complicated issue as we have four completely seperate domains on site. They all need to talk to each other but each has its own DNS and DHCP.

I was instructed to get a layer 3 managed switch and purchased the SG300-10. The ISP has configured the router (C1921) with four default gateways and tagged each one. I understand the tagging of Vlans and how to allocate the ports. Where i am a little stuck is the interconnection between C1921 and SG300-10 to allow internet connection to all Vlans. I have looked for information everywhere but had little success. The main problem seems to be no connectivity from SG300-10 to router, none of the gateways are pingable from SG300-10. I am guessing my issue is i need to setup a port for the router connection ? How do I achieve this ?

Sorry if this question is a little dumb, never had to use managed switching before and there is a slight learning curve.

I appreciate any help you guys could supply.




VIP Purple

Hey so they have configured 4

Hey so they have configured 4 gateways for each vlan all set under 1 physical interface on the 1921 is that correct ?  If thats the case you only needed a layer 2 switch as its a router and stick setup and your side trunked

Your switch port connecting to the router needs to be a trunk allowing all layer 2 vlans up to it

heres a concept should be easy to follow if thats what they have done.

If its not that and its pure layer 3 between the router and switch they should have provided more info like the IGP there using so you can form to it



You need to connect your switch to C1921. I suppose you connect interface GE28 to 1921.

Follow these steps


You need to create 4 VLANs. The VLAN-IDs must be the same as 1921 IDs.

configure terminal

      VLan 10

       vlan 20

       vlan 30

       vlan 40


Interface GE28 [Please check interfaces names ]

descrition connects to 1921

switchport encapsulation dot1q

switchport mode trunk

3- You need to group your computers and assign them to to each VLAN. You may use only one vlan for everyone depending on your policy. I suppose you have 5 computers assigning to VLAN 10. Their default Gateway corresponding to VLAN 10 is set on 1921 .

I suppose is set on 1921 for VLAN 10

interface range gi1-5 

switchport mode access

switchport access VLAN 10

[ configure computer 1 IP with default gateway]

[ configure computer 2  IP with default gateway]

and so on

6 computer in VLAN 20

I suppose is set on 1921 for VLAN 20

interface range gi6-11

switchport mode access

switchport access VLAN 20

[ computer 6 with default gateway]

[ computer 7 with default gateway]

and so on

You need to countinue addnig other two vlans .

It is very simple.

Hope it helps,


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