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New Member

Routing from Gigabit Ethernet 0/0 thru to allow internet access?

Dear all,

We've finally got our Cisco 1941 onto the internet (which is great) but can anyone advise us on how to configure routing from this interface to the serial interface so we can access the internet from our LAN?

Kind Regards,

Noaman

10 REPLIES

Re: Routing from Gigabit Ethernet 0/0 thru to allow internet acc

Well congrate..

You want to access internet from LAN via. serial interface If so

Int gig0/0

ip address 10.10.10.1 255.255.255.0  <<< IP address of LAN

no shut

int serial0/0

ip address 192.168.14.1 255.255.255.252 <

ip route 0.0.0.0 0.0.0.0  serial0/0  << Default route pointing toward provider

If you are running bgp in place of static routing the config will be little different

Hope this helps

Regards

Mahesh

New Member

Re: Routing from Gigabit Ethernet 0/0 thru to allow internet acc

Hi Mahesh,

Thank you for such a quick response, we've been advised to use bgp, what command would we use to allow a PC/Lan connected to Gigabit 0/0 to access the internet via Serial 0/0/0:0?

Thank you,

Noaman

Re: Routing from Gigabit Ethernet 0/0 thru to allow internet acc

Thanks for your clarification

Well provider will provide default route in bgp..so the config will be much simple

router bgp

neighbor w.w.w.w remote-as     <<< w.w.w.w will be wan ip address configured at provider end

no syncronisation

network mask    <<< x.x.x.x will be your lan ip configured on gig link with subnet mask

that't it.

you can verify the default route learned from provider via. sh ip bgp neighbor routes.

Hope this helps

Regards

Mahesh

New Member

Re: Routing from Gigabit Ethernet 0/0 thru to allow internet acc

Thanks Mahesh,

It appears to have taken the commands but I did have to enter 'network x.x.x.0 mask x.x.x0 then it took the commands ok

But when I use CP to test the connection I get this error 'there is no configured route to any of the DNS servers through the selected interface' Do I also need to add another route to DNS?

Thank,

Noam

Hall of Fame Super Silver

Re: Routing from Gigabit Ethernet 0/0 thru to allow internet acc

Noam

It seems to me that there are 2 possibilities:

- CP is looking for configured routes and does not recognize the dynamic route from BGP.

- there is a problem with the BGP that you configured.

It would be helpful if you would post the output of show ip route. This will tell us for sure whether you are learning the default route via BGP.

HTH

Rick

New Member

Re: Routing from Gigabit Ethernet 0/0 thru to allow internet acc

Ok thank Rick, here's the results:

NTRouter#
NTRouter#
NTRouter#
NTRouter#sho
NTRouter#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, + - replicated route

Gateway of last resort is 0.0.0.0 to network 0.0.0.0

S*    0.0.0.0/0 is directly connected, Serial0/0/0:0
      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        10.10.10.0/29 is directly connected, GigabitEthernet0/0
L        10.10.10.1/32 is directly connected, GigabitEthernet0/0
      109.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C        x.x.x.x/30 is directly connected, GigabitEthernet0/1
L        x.x.x.x/32 is directly connected, GigabitEthernet0/1
C        x.x.x.x/30 is directly connected, Serial0/0/0:0
L        x.x.x.x/32 is directly connected, Serial0/0/0:0   <<
NTRouter#

Thanks,

Noam

Hall of Fame Super Silver

Re: Routing from Gigabit Ethernet 0/0 thru to allow internet acc

Noam

Thank you for posting the additional information. It is helpful, but still does not get us a full answer to the question.

The show ip route does not show that any routes (and especially no default route) are learned via BGP. So that makes me think that something may be a problem about BGP. Would you post the output of show ip bgp summ and perhaps also the output of show ip bgp neighbor

But the output of show ip route does show a static default route. It is probably configured as ip route 0.0.0.0 0.0.0.0 serial0/0/0:0. Is that correct. Since there seems to be a valid default route I am puzzled why CP does not recognize it.

HTH

Rick

New Member

Re: Routing from Gigabit Ethernet 0/0 thru to allow internet acc

Here's the results Rick:


NTRouter#show ip bgp summ
BGP router identifier x.x.x.x, local AS number 65530 <<
BGP table version is 3, main routing table version 3
1 network entries using 120 bytes of memory
1 path entries using 52 bytes of memory
1/1 BGP path/bestpath attribute entries using 124 bytes of memory
1 BGP AS-PATH entries using 24 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 320 total bytes of memory
BGP activity 1/0 prefixes, 1/0 paths, scan interval 60 secs

Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State       /PfxRcd
x.x.x.x  4        20500     217     239        3    0    0 03:34:31               1  <<
NTRouter#

______________________ More info below:


NTRouter#show ip bgp neighbors
BGP neighbor is x.x.x.x,  remote AS 20500, external link <<  BGP version 4, remote router ID 109.204.34.253
  BGP state = Established, up for 03:37:33
  Last read 00:00:29, last write 00:00:34, hold time is 180, keepalive interval is 60 seconds
  Neighbor sessions:
    1 active, is not multisession capable
  Neighbor capabilities:
    Route refresh: advertised and received(new)
    Four-octets ASN Capability: advertised and received
    Address family IPv4 Unicast: advertised and received
    Graceful Restart Capability: received
      Remote Restart timer is 120 seconds
      Address families advertised by peer:
        IPv4 Unicast (was preserved)
    Multisession Capability: advertised
  Message statistics:
    InQ depth is 0
    OutQ depth is 0

                         Sent       Rcvd
    Opens:                  1          1
    Notifications:          0          0
    Updates:                1          2
    Keepalives:           240        217
    Route Refresh:          0          0
    Total:                242        220
  Default minimum time between advertisement runs is 30 seconds

For address family: IPv4 Unicast
  Session: x.x.x.x <<  BGP table version 3, neighbor version 3/0
  Output queue size : 0
  Index 1
  1 update-group member
                                 Sent       Rcvd
  Prefix activity:               ----       ----
    Prefixes Current:               0          1 (Consumes 52 bytes)
    Prefixes Total:                 0          1
    Implicit Withdraw:              0          0
    Explicit Withdraw:              0          0
    Used as bestpath:             n/a          1
    Used as multipath:            n/a          0

                                   Outbound    Inbound
  Local Policy Denied Prefixes:    --------    -------
    Bestpath from this peer:              2        n/a
    Total:                                2          0
  Number of NLRIs in the update sent: max 0, min 0

  Address tracking is enabled, the RIB does have a route to x.x.x.x <<  Connections established 1; dropped 0
  Last reset never
  Transport(tcp) path-mtu-discovery is enabled
  Graceful-Restart is disabled
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Connection is ECN Disabled, Mininum incoming TTL 0, Outgoing TTL 1
Local host: x.x.x.x, Local port: 55465 <<
Foreign host: x.x.x.x, Foreign port: 179 <<Connection tableid (VRF): 0
Maximum output segment queue size: 50

Enqueued packets for retransmit: 0, input: 0  mis-ordered: 0 (0 bytes)

Event Timers (current time is 0x2079EE60):
Timer          Starts    Wakeups            Next
Retrans           242          0             0x0
TimeWait            0          0             0x0
AckHold           220        213             0x0
SendWnd             0          0             0x0
KeepAlive           0          0             0x0
GiveUp              0          0             0x0
PmtuAger            1          1             0x0
DeadWait            0          0             0x0
Linger              0          0             0x0
ProcessQ            0          0             0x0

iss: 2960402761  snduna: 2960407403  sndnxt: 2960407403     sndwnd:  11680
irs: 3543097407  rcvnxt: 3543101665  rcvwnd:      16346  delrcvwnd:     38

SRTT: 300 ms, RTTO: 303 ms, RTV: 3 ms, KRTT: 0 ms
minRTT: 12 ms, maxRTT: 300 ms, ACK hold: 200 ms
Status Flags: active open
Option Flags: nagle, path mtu capable
IP Precedence value : 6

Datagrams (max data segment is 1400 bytes):
Rcvd: 458 (out of order: 0), with data: 220, total data bytes: 4257
Sent: 460 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 0), with data: 242, total data bytes: 4641
Packets received in fast path: 0, fast processed: 0, slow path: 0
fast lock acquisition failures: 0, slow path: 0

Thanks again Rick your help is appreciated,

Noam

Hall of Fame Super Silver

Re: Routing from Gigabit Ethernet 0/0 thru to allow internet acc

Noam

Thank you for the additional information. Based on information in the thread so far I believe that this is the situation:

- BGP is configured, running, and has successfully established a neighbor relationship with the ISP.

- the ISP is advertising one prefix to you, and probably that is a default route. The output of show ip bgp would be a good way to verify that.

- the prefix advertised from the ISP is not in the routing table. This is because of the locally configured static default route.

- it appears that you are not advertising anything to the ISP. This would not matter if your packets from inside are being translated using the serial address with overload.

In the beginning of this thread the problem was that testing with CP was reporting a probleml. Is that still the case?

It looks to me that you have a successful routing environment for access to the Internet, especially assuming that address translation is correctly configured. I believe that there is a question which should be resolved and it is the question of the default route advertised from the ISP and the locally configured static default route. If you have a BGP default route then you would not need the static default route. And if you have the static default route then you do not need theBGP default route. So which one do you want to use?

HTH

Rick

Hall of Fame Super Silver

Re: Routing from Gigabit Ethernet 0/0 thru to allow internet acc

Noam

I read through the thread again and realized that in the output of show ip route it indicates that your Gig interface has an address in the 109.0.0.0 network. So my comments in my previous post about network address translation may be off the mark. Is there is something connected to the Gig interface (probably a firewall or something) that is already translating your inside addresses?

And if your addresses are being translated using the addressing of the Gig interface, then the question of whether you are advertising a prefix to the ISP becomes more important. So please do post the output of show ip bgp.

HTH

Rick

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