Solved: Re: Noob and his Ebay 831 Router - Page 2

Chris Simon · ‎11-27-2013

I picked up an 831 Ethernet Router for 5$ on ebay just to set up two static IPs on my home network--simple boring. The manual says to hook up my PC one of the ethernet ports and set it to DHCP. This returns a odd DHCP value, 169.254.92.156 or 169.254.50.157. I expected 10.10.10.x

What do you think is going on? Did the last owner config the router with this strange subnet? Or is it borked?

Can I reset the modem without having to get the console cable?

What's more, I assumed this router could set up basic NAT static IP for the ethernet ports. But the manual only mentions DHCP. Searches on NAT and static IP didn't return any How-To or other useful getting started links.

The network is very simple. I have a cable modem and two PCs I want on this router. Any reason I can't expect to fix this?

cadet alain · ‎01-02-2014

Hi,

enable

config t

then type all commands I gave.

all commands under int e1 and int vlan 1 are interface config commands

when in global config type int x to get into interface config mode

you have no router config commands here and others are global config commands which put you in some submodes.

the mode you're in is in the prompt in parenthesis.

Regards

Alain

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Chris Simon · ‎01-02-2014

@cadet alain,

ip address x.x.x.x x.x.x.x  // IP address in same subnet as ISP modem

This is not a static IP. Its dynamic--this value will change. I'm sorry if I didn't make that clear from the beginning.

cadet alain · ‎01-02-2014

Hi,

sorry I gave you wrong command, it is ip address dhcp as your isp modem is dhcp server.

Regards

Alain

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Chris Simon · ‎01-02-2014

@cadet alain,

Turns out IOS 12.2 doesn't have several of these commands. For the first example, I think I found a substitute:

     ? ip dhcp client client-id ethernet1         // this appears to be IOS 12.4 [[1]] 
     # ip address dhcp client-id ethernet1    // I changed it to this [[2]]

Unfortunately I can't find a substitute for vlan in 12.2 documentation [[2]].

? int vlan 1                    // this command won't work
# ip address 10.10.10.1 255.255.255.0          // router ip
# ip nat inside               // NAT
/** I see the "excluded-address" reflects the four ethernet ports which I hope to use static 10.10.10.2-5. Why `mypool`? There's no DHCP addresses in this config. Delete this section? 
**/
# ip dhcp excluded-address 10.10.10.1 10.10.10.5
# no ip dhcp conflict logging
# ip dhcp pool mypool
# network 10.10.10.0 255.255.255.0       // back to the router
# default-router 10.10.10.1
/** This block is the planned DDNS? As you suggested above, put this off until NAT is working. Delete?
**/
# dns-server x.x.x.x   where x.x.x.x is ISP cable modem IP address
# access-list 1 permit 10.10.10.0 0.0.0.255
/** Back to the NAT config **/
# ip nat inside source list 1 interface ethernet1
# ip nat inside source static tcp 10.10.10.2 80 interface ethernet1 80

Again, I'm a noob so getting these bold sections to map onto the 12.2 NAT config I found here [[3]] on site is blowing my mind,

# ip nat inside source static local-ip  global-ip 
# interface type number
# ip nat inside
# interface type number 
# ip nat outside

[1]: http://www.cisco.com/en/US/docs/ios-xml/ios/ipaddr_dhcp/configuration/12-4t/config-dhcp-client.html

[2]: http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfdhcp.html

[3]: http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfipadr.html/vlan

pieterh · ‎01-03-2014

>>> ? int vlan 1 // this command won't work <<<

That will be because the router is only a router, not a switch

the 4-port switch built into this router does not support multiple VLAN's

>>>

Why `mypool`? There's no DHCP addresses in this config. Delete this section?

**/

# ip dhcp excluded-address 10.10.10.1 10.10.10.5

# no ip dhcp conflict logging

# ip dhcp pool mypool

# network 10.10.10.0 255.255.255.0 // back to the router

# default-router 10.10.10.1

<<<

These commands setup the router as dhcp server for the LAN ports.

If you use only static adresses here you can remove all references

The default-router command used here defines the default router for the dhcp clients in this pool / network 10.10.10.0/24

you can also assign other dhcp-options heer like a nameserver or dns domain-suffix for the clients.

the exclude command reserves space for the router address itself (10.10.10.1) and some room for other static adresses.

pieterh · ‎01-03-2014

by the way,

the reason for not getting a dhcp-address may be caused by the autonegotiate handshake between client and router.

In some situations the dhcp-request on the client times out before the speed/duplex negotiation has finished, or because this handshake has resulted in a mismatch.

try setting speed/duplex fixed -> NB! either BOTH sides fixed or both sides auto.

Chris Simon · ‎01-03-2014

@pieterh

...you can also assign other dhcp-options heer like a nameserver or dns domain-suffix for the clients.

is a DHCP pool necessary for DDNS (Dynamic DNS)?

I shouldn't think so, but I an a noob.

----

Also, Found another set-up for IOS 12.0 for modem to 805 router with very explict instructions--very noob friendly (^_^)

(http://www.cisco.com/en/US/tech/tk175/tk15/technologies_configuration_example09186a0080093e51.shtml)

PS. I just noticed my replies are running out of <------> room!!

//redundant

pieterh · ‎01-05-2014

>>>

is a DHCP pool necessary for DDNS (Dynamic DNS)?

I shouldn't think so, but I an a noob.

<<<

the DHCP pool is for the local lan

DDNS is needed for the public internet to find you by name.especially if your provider issues you changing adresses (dhcp on provider side).

if you have got a fixed address at your provider, then you can register a fixed DNS entry.

Chris Simon · ‎01-14-2014

We've discussed quite a few things here, the AP is a DHCP server, inside local addresses are static (and not DHC)P, and no vlan for this 831 that's not a switch. I've edited the original recommended commands but there are still a few questions (n).

Router> enable
Router(config)# conf t                                       
Router(config)# int e1
Router(config)# description ToCableModem
Router(config)# ip address dhcp client-id ethernet1       
Router(config)# ip nat outside
Router(config)# no shutdown
/** (1) Delete this since this doesn't do vlan?
Router(config)# int vlan                                    
Router(config)# ip address 10.10.10.1 255.255.255.0
Router(config)# ip nat inside
**/
/** (2) delete this as per pieterh...?
# ip dhcp excluded-address 10.10.10.1 10.10.10.5
# no ip dhcp conflict logging
# ip dhcp pool mypool
**/
/** (3) Is this complete BS? **/
Router(config)# ip nat inside source static 10.10.10.10.2 dhcp
Router(config)# ip nat inside source static 10.10.10.10.3 dhcp
Router(config)# ip nat inside source static 10.10.10.10.4 dhcp
Router(config)# ip nat inside source static 10.10.10.10.5 dhcp
Router(config)# interface ethernet1
Router(config-if)# ip nat inside
Router(config)# interface ethernet0
Router(config-if)# ip nat outside
Router(config)# network 10.10.10.0 255.255.255.0
Router(config)# default-router 10.10.10.1

Is this enough to simply map the inside local addresses to the inside global address (dynamic IP at the cable model, right?)

My cisco-vocabulary is improving. Learn something new--again!

pieterh · ‎01-14-2014

no this line wont work

Router(config)# ip nat inside source static 10.10.10.10.2 dhcp

change the "dhcp" to "interface Ethernet0 overload"

this tells rhe router to use the adress of the outside interface for NAT.

more flexible would be to use an access-list

access-list 102 permit ip 10.10.10.10.0 0.0.0.255 any

route-map INTERNET permit 10
match ip address 102

ip nat inside source route-map INTERNET interface Ethernet0 overload

by tuning the access list you can select wich hosts can do NAT for outgoing traffic.

Chris Simon · ‎01-16-2014

I did a quick search for this "access list NAT for outbound traffic". I see the issue is quite extensive and relevant [1] [2] Of course, these links are from the initiated. I'm not sure why my hosts would be "do(ing) NAT for outgoing trarric". I thought I was setting up the router to do this...? And reading another Cisco page has this comment on access lists:

Inbound and Outbound Access List Overview
 By default, all traffic from a higher-security interface to a  lower-security interface is allowed. Access lists let you either allow  traffic from lower-security interfaces, or restrict traffic from  higher-security interfaces. [3]

Shouldn't I want to allow traffic from higher-security (my home network) to lower security (the world) by default, therefore all hosts? Does that make sense?

cadet alain · ‎01-20-2014

Hi,

The link you provided the exerpt from is for an ASA which is a firewall not for a router.

By default routers don't filter any traffic whether it be from LAN to WAN or from WAN to LAN but if you use RFC1918 in your LAN then you need NAT( dynamic for LAN to WAN and return) or static for WAN to LAN(and return as the private IP addresses are non routeable on the Internet.

Regards

Alain

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pieterh · ‎01-22-2014

my formulation is wrong,
What I meant is not the hosts do nat,
But the hosts are alowed to be NATted by the router.

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