Hello,

Hope to find help here, got stupid already.. Have changed ISP lately,
received new ADSL modem (Zyxel), connected it to own cisco 1750 and..


1. When logged on to cisco:

- Trying to ping any external host for first time causing first 4-5
packets to be lost; trying to ping same host again giving 0% packets
lost, but.. if I would wait some time (about a hour-two) fun will start
again, first ping will lose 4-5 packets, next pings will be ok. It is not
DNS problem - have tested 4 of them, also for tests I am using IP, not
DNS name.
- Cisco has 2 interfaces, internal (lan) and external (wan); trying to
extelnal interface's IP is not successful (100% packets lost), while
pinging ADSL modem's IP (last octet is one digit lower) works fine.


2. When working on LAN-connected notebook:

- Pinging behaves in same way as described above
- Opening any web page takes _long_ time, sometimes I need to refresh
content once or twice to see it finally
- Opening ssh session to external host is not always successful


3. From external world:

- Pinging to Cisco's external IP from external host behaves in same way
as described above.


4. Additionally:

- Cisco harwdware seems to be ok - I have 1750 and 1751, thinking 1750 is
faulted have used 1751. Behavior was same.
- On external Cisco interface I have low number of errors reported (few
errors per between thousands ok); moreover, errors are only on interface
connected to ADSL (have switched configuration to check).

help. most basic configuration of those used is below.

===========

Current configuration : 1118 bytes
!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname c1750
!
boot-start-marker
boot-end-marker
!
enable secret 5 $1$2O0f$6NIoN1i8TAqM0zi5llIdr0
enable password xxx
!
no aaa new-model
no ip subnet-zero
!
!
!
ip dhcp pool local
network 10.0.0.0 255.0.0.0
domain-name xxx
dns-server 217.8.168.244
default-router 10.0.0.1
!
!
ip name-server 217.8.168.244
! tried with & without it: ip cef
no scripting tcl init
no scripting tcl encdir
!
!
!
!
interface Ethernet0
ip address 10.0.0.1 255.0.0.0
ip nat inside
half-duplex
! tried with & without; with is better, but still bad: arp timeout 172800
!
interface FastEthernet0
ip address 89.x.x.x 255.255.255.252
ip nat outside
speed auto
! tried with & without; with is better, but still bad: arp timeout 172800
!
ip nat inside source list 1 interface FastEthernet0 overload
ip classless
ip route 0.0.0.0 0.0.0.0 FastEthernet0
ip route 10.0.0.0 255.0.0.0 Ethernet0
no ip http server
!
!
access-list 1 permit 10.0.0.0 0.255.255.255
access-list 1 permit 89.x.x.x 0.0.0.4
!
control-plane
!
!
line con 0
line aux 0
line vty 0 4
password xxx
login
!
no scheduler allocate
!
end