I had a problem with my VACL configuration on cisco packet tracer.
My problem is I want to block ping to 192.168.6.2 from 192.168.1.0 but it keeps failing
Here is my code :
access-list 101 deny icmp 192.168.6.2 0.0.0.0 192.168.1.0 0.0.0.255 echo-reply
access-list 101 permit icmp any any
interface gig0/0/0
ip access-group 101 in
ex
my network picture
You swapped between source and destination adresses :
Access-list 101 deny icmp 192.168.1.0 0.0.0.255 host 192.168.6.2 echo
Related
I have an OdroidH2 with docker setup.
It was working fine for a few months and suddenly, out of nowhere it stopped having any internet/intranet connectivity.
It's connectivity is going through an Ethernet cable, not WiFi and the interface that is supposed to have the connection is enp3s0 with an ip address of 192.168.1.100.
I have performed the following troubleshooting steps:
Restart (of course, always the first step)
Checked interface settings via ifconfig and also in /etc/network/interfaces
Checked the routing via route -n
Checked iptables (iptables was populated with the docker configuration, I've flushed the iptables including nat and mangle and set the default policy to ACCEPT for input, forward and output. Restarted the networking service afterwards)
Checked if it was able to ping itself and the default gateway (it is able to ping itself but not the gateway, or any other devices)
Checked if another device was able to ping the OdroidH2 (host unreachable)
Checked dmesg and for some reason, I had 2 firmwares that were not able to be loaded (already installed and rebooted after installation):
rtl_nic/rtl8168g-2.fw (after checking, this is the firmware for the network interfaces)
i915/glk_dmc_ver1_04.bin (didn't research much about this one, something to do with runtime power management??)
After all of these steps, I still am unable to get the network connectivity going.
Below you can find information regarding my current configuration:
dmesg output
Stackoverflow does not allow me to put all the information from my dmesg output so I had to put it on google drive: dmesg_output
/etc/hosts
127.0.0.1 localhost
192.168.1.100 dc1 dc1.samdom.andrewoliverhome.local samdom.andrewoliverhome.local
# The following lines are desirable for IPv6 capable hosts
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
iptables -nvL output (after clearing and reloading the networking service)
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
/etc/resolv.conf
#nameserver 127.0.0.1
#nameserver 8.8.8.8
#nameserver 8.8.4.4
search samdom.andrewoliverhome.local
#domain samdom.andrewoliverhome.local
nameserver 192.168.1.100
nameserver 8.8.8.8
route -n output
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.1.254 0.0.0.0 UG 0 0 0 enp3s0
172.17.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker0
172.18.0.0 0.0.0.0 255.255.0.0 U 0 0 0 docker_gwbridge
172.19.0.0 0.0.0.0 255.255.0.0 U 0 0 0 br-debc10cb5b21
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 enp3s0
/etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
source /etc/network/interfaces.d/*
# The loopback network interface
auto lo enp2s0 enp3s0
#auto lo br0
iface lo inet loopback
# The primary network interface
iface enp2s0 inet dhcp
allow-hotplug enp2s0 enp3s0
#iface enp2s0 inet manual
# post-up iptables-restore < /etc/iptables.up.rules
# This is an autoconfigured IPv6 interface
#iface enp2s0 inet dhcp
iface enp3s0 inet static
address 192.168.1.100
netmask 255.255.255.0
# broadcast 169.254.99.255
network 192.168.1.0
gateway 192.168.1.254
#iface enp2s0 inet manual
#iface enp3s0 inet manual
#iface br0 inet static
# bridge_ports enp2s0 enp3s0
# address 192.168.1.100
# broadcast 192.168.1.255
# netmask 255.255.255.0
# gateway 192.168.1.254
#
In /etc/resolv.conf, the reason I have the primary nameserver to be itself is because I am running a docker container that is serving as a samba-ad-dc.
In order for OdroidH2 to find all of my devices in the domain, it needs to make dns queries to the samba dc, if samba is not able to find a dns record, it will autoforward it to 8.8.8.8.
Any help would be greatly appreciated (:
After all the troubleshooting done, the issue is not within the OdroidH2 itself, it was with my router.
The LAN port that I'm using malfunctioned. I switched the Ethernet cable to a different LAN port and it worked.
I have a server. I want to make possible sending requests to this server from the internet (this works) and simultaneously block requests from the server to domains.
I want to type
ping google.com
on the server and see nothing.
Now I see
ping google.com
PING google.com (216.58.205.46) 56(84) bytes of data.
64 bytes from mil04s24-in-f46.1e100.net (216.58.205.46): icmp_seq=1 ttl=54 time=36.3 ms
64 bytes from mil04s24-in-f46.1e100.net (216.58.205.46): icmp_seq=2 ttl=54 time=63.7 ms
You can block any tcp / udp outgoing traffic using the iptables firewall rules.
For example, you can block any outgoing TCP traffic from port 5050 with below firewall rule -
iptables -A OUTPUT -p tcp --dport 4050 -j DROP
iptables save
Similarly to block ping request, you can block ICMP protocol for any outbound traffic.
I'm trying to programmatically construct and send IP packet through TUN device.
I've setup the TUN device and proper routes:
# ip tuntap add mode tun tun0
# ip link set tun0 up
# ip addr add 10.0.0.2/24 dev tun0
which results in:
$ route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use
Iface
0.0.0.0 192.168.0.1 0.0.0.0 UG 600 0 0 wlp3s0
10.0.0.0 0.0.0.0 255.255.255.0 U 0 0 0 tun0
192.168.0.0 0.0.0.0 255.255.255.0 U 600 0 0 wlp3s0
$ ifconfig tun0
tun0: flags=4241<UP,POINTOPOINT,NOARP,MULTICAST> mtu 1500
inet 10.0.0.2 netmask 255.255.255.0 destination 10.0.0.2
inet6 fe80::f834:5267:3a1:5d1d prefixlen 64 scopeid 0x20<link>
unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 500 (UNSPEC)
IP forwarding is ON: # echo 1 > /proc/sys/net/ipv4/ip_forward
I've setup NAT for tun0 packets:
# iptables -t nat -A POSTROUTING -s 10.0.0.0/24 -o wlp3s0 -j MASQUERADE
# iptables -t nat -L -v
Chain POSTROUTING (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
0 0 MASQUERADE all -- any wlp3s0 10.0.0.0/24 anywhere
Then I have python script to produce ICMP packets:
import os
from fcntl import ioctl
import struct
import time
import random
# pip install pypacker==4.0
from pypacker.layer3.ip import IP
from pypacker.layer3.icmp import ICMP
TUNSETIFF = 0x400454ca
IFF_TUN = 0x0001
IFF_NO_PI = 0x1000
ftun = os.open("/dev/net/tun", os.O_RDWR)
ioctl(ftun, TUNSETIFF, struct.pack("16sH", b"tun0", IFF_TUN | IFF_NO_PI))
req_nr = 1
req_id = random.randint(1, 65000)
while True:
icmp_req = IP(src_s="10.0.0.2", dst_s="8.8.8.8", p=1) +\
ICMP(type=8) +\
ICMP.Echo(id=req_id, seq=req_nr, body_bytes=b"povilas-test")
os.write(ftun, icmp_req.bin())
time.sleep(1)
req_nr += 1
I can see packets originating from tun0 interface:
# tshark -i tun0
1 0.000000000 10.0.0.2 → 8.8.8.8 ICMP 48 Echo (ping) request id=0xb673, seq=1/256, ttl=64
2 1.001695939 10.0.0.2 → 8.8.8.8 ICMP 48 Echo (ping) request id=0xb673, seq=2/512, ttl=64
3 2.003375319 10.0.0.2 → 8.8.8.8 ICMP 48 Echo (ping) request id=0xb673, seq=3/768, ttl=6
But wlp3s0 interface is silent, thus it seems that packets don't get NAT'ed and routed to wlp3s0 interface, which is my WLAN card.
Any ideas what I am missing?
I'm running Debian 9.
And turns out that packet forwarding was disabled - default policy for FORWARD chain is DROP:
# iptables -L -v
Chain FORWARD (policy DROP 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
So I changed the policy:
# iptables -P FORWARD ACCEPT
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Also, I had to change the IP packet source address to something other than 10.0.0.2 which is the preferred source address for tun0 interface:
$ ip route
10.0.0.0/24 dev tun0 proto kernel scope link src 10.0.0.2
So I changed the packet source address to 10.0.0.4:
icmp_req = IP(src_s="10.0.0.4", dst_s="8.8.8.8", p=1) +\
ICMP(type=8) +\
ICMP.Echo(id=req_id, seq=req_nr, body_bytes=b"povilas-test")
Then kernel started forwarding packets coming from tun0 interface to the gateway interface:
# tshark -i wlp3s0
5 0.008428567 192.168.0.103 → 8.8.8.8 ICMP 62 Echo (ping) request id=0xb5c7, seq=9/2304, ttl=63
6 0.041114028 8.8.8.8 → 192.168.0.103 ICMP 62 Echo (ping) reply id=0xb5c7, seq=9/2304, ttl=48 (request in 5)
Also ping responses were sent back to tun0:
# tshark -i tun0
1 0.000000000 10.0.0.4 → 8.8.8.8 ICMP 48 Echo (ping) request id=0xb5c7, seq=113/28928, ttl=64
2 0.035470191 8.8.8.8 → 10.0.0.4 ICMP 48 Echo (ping) reply id=0xb5c7, seq=113/28928, ttl=47 (request in 1)
I'm newbie in networking field. I have trouble with my web server Network configuration (OS is Centos).
I have 2 NICs (eth0 + eth2 - physically) running 2 public IP which have the same subnet, same gateway.
When I configure nginx to listen on these 2 NICs, everything works just fine. But when I monitor the traffic, all traffic is on the eth0 only, nothing on eth2.
My question is: How can I configure so that traffic goes in a NIC, go out on that NIC, too?
This is my ethernet card config:
DEVICE="eth0"
ONBOOT=yes
BOOTPROTO=static
IPADDR=x.x.x.38
PREFIX=27
GATEWAY=x.x.x.x.33
DNS1=8.8.8.8
DNS2=8.8.4.4
NAME="System eth0"
DEVICE="eth2"
ONBOOT=yes
BOOTPROTO=static
IPADDR=x.x.x.39
PREFIX=27
GATEWAY=x.x.x.33
DNS1=8.8.8.8
DNS2=8.8.4.4
NAME="System eth2"
This is my route -n result
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.14.8.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
y.z.0.0 0.0.0.0 255.255.0.0 U 1002 0 0 eth0
y.z.0.0 0.0.0.0 255.255.0.0 U 1003 0 0 eth1
y.z.0.0 0.0.0.0 255.255.0.0 U 1004 0 0 eth2
0.0.0.0 x.x.x.33 0.0.0.0 UG 0 0 0 eth0
Hope you can help, thanks in advanced!
In Linux, routing is performed by looking at the destination address only, so a packet will follow whichever route can be used to reach the packet's destination, with no regard to the source address.
The behaviour you want requires choosing a route depending not only on the destination address, but also on the source address — this is sometimes called source-sensitive routing or SADR (source-address dependent routing). The most portable way of implementing source-sensitive routing under Linux is to define routing rules across multiple routing tables using the ip rule and ip route ... table ... commands.
This is described in detail in Section 4 of the Linux Advanced Routing and Traffic Control HOWTO
Probably, the problem can be solved even with NAT.
ip tuntap add dev tap0 mode tap
ip tuntap add dev tap1 mode tap
Then you can assign separate ip addresses to these devices:
ifconfig tap0 10.10.10.1 netmask 255.255.255.255
ifconfig tap1 10.10.10.2 netmask 255.255.255.255
And finally - redirect incoming traffic to specific virtual device
iptables -t nat -A PREROUTING -i eth0 -j DNAT --to-destination 10.10.10.1
iptables -t nat -A PREROUTING -i eth2 -j DNAT --to-destination 10.10.10.2
In this case, all traffic will be routed definetely to the interface it came from.
I'm trying to test a gateway I wrote(see What's the easiest way to test a gateway? for context). Due to an issue I'd rather not get into, the gateway and "sender" have to be on the same machine. I have a receiver(let's say 9.9.9.9) which the gateway is able to reach.
So I'll run an application ./sendStuff 9.9.9.9 which will send some packets to that IP address.
The problem is: how do I get the packets destined for 9.9.9.9 to go to the gateway on localhost? I've tried:
sudo route add -host 9.9.9.9 gw 127.0.0.1 lo
sudo route add -host 9.9.9.9 gw <machine's external IP address> eth0
but neither of those pass packets through the gateway. I've verified that the correct IPs are present in sudo route. What can I do?
Per request, here is the route table, after running the second command(IP addresses changed to match the question. x.y.z.t is the IP of the machine I'm running this on):
Destination Gateway Genmask Flags Metric Ref Use Iface
9.9.9.9 x.y.z.t 255.255.255.255 UGH 0 0 0 eth0
x.y.z.0 0.0.0.0 255.255.254.0 U 0 0 0 eth0
0.0.0.0 <gateway addr> 0.0.0.0 UG 100 0 0 eth0
127.0.0.1 is probably picking up the packets, then forwarding them on their merry way if ipv4 packet forwarding is enabled. If it's not enabled, it will drop them.
If you are trying to forward packets destined to 9.9.9.9 to 127.0.0.1, look into iptables.
Edit: try this:
iptables -t nat -A OUTPUT -d 9.9.9.9 -j DNAT --to-destination 127.0.0.1
That should redirect all traffic to 9.9.9.9 to localhost instead.