the ifconfig output of my machine is the following:
:~ shell$ ifconfig en0
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether 00:25:bc:e7:39:6a
inet6 fe80::225:bcff:fee7:396a%en0 prefixlen 64 scopeid 0x4
inet 10.170.133.45 netmask 0xffffff00 broadcast 10.170.133.255
media: autoselect (100baseTX <full-duplex>)
status: active
I know that netmask 0xffffff00 is the hexadecimal representation of 255.255.255.0.
But which is the correct way of converting that string into the octet format?
Can you suggest some unix command or shell script?
say you already gotten that hex number into a variable
$ s="0xffffff00"
$ p="${s:0:2}"
$ printf "%d.%d.%d.%d\n" ${p}${s:2:2} ${p}${s:4:2} ${p}${s:6:2} ${p}${s:8:2}
255.255.255.0
Related
My plan is to read from one tun interface and write to another.
Here are my command when I set up the interface:
sudo ip tuntap add dev router0 mod tun
sudo ip addr add 10.0.0.138/24 dev router0
sudo ip link set dev router0 up
Here is the output of ip addr show dev router0
8: router0: <NO-CARRIER,POINTOPOINT,MULTICAST,NOARP,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 500
link/none
inet 10.0.0.138/24 scope global router0
valid_lft forever preferred_lft forever
When I try to ping 10.0.0.138 listen on the interface using tshark via sudo tshark -i router0, nothing happens.
Here is my ping 10.0.0.138 output:
PING 10.0.0.138 (10.0.0.138) 56(84) bytes of data.
64 bytes from 10.0.0.138: icmp_seq=1 ttl=64 time=0.063 ms
64 bytes from 10.0.0.138: icmp_seq=2 ttl=64 time=0.058 ms
Here is my sudo tshark -i router0 output:
Capturing on 'router0'
Nothing is coming through
What is the problem?
How to get connected machine's IP and Mac of SNMP device.
ARP cache is not giving correct details.
Example for Linux shell commands (no tag for other languages or Windows at time of writing)
Providing that the machine you want to query does run a SNMP Daemon ( generally snmpd from Net-SNMP under Linux ) and that you know how/are allowed to speak to it ( version 1, 2c or 3 with various community names or usernames/passwords/encoding for v3 ) you may issue the following SNMP requests:
For the test I started a snmpd on a CentOS 7 virtual machine whose main address was 192.168.174.128.
I choose port 1610 over the traditional 161 in order not to sudo or to setcap (snmpd). The snmpd.conf file contents is out of the range of this question.
This first one for IPs
snmptable -v 2c -c private 192.168.174.128:1610 ipAddrTable
SNMP table: IP-MIB::ipAddrTable
ipAdEntAddr ipAdEntIfIndex ipAdEntNetMask ipAdEntBcastAddr ipAdEntReasmMaxSize
127.0.0.1 1 255.0.0.0 0 ?
192.168.122.1 3 255.255.255.0 1 ?
192.168.174.128 2 255.255.255.0 1 ?
The second command (with 3 columns only printed) for MAC
snmptable -v 2c -c private 192.168.174.128:1610 ifTable | awk -c '{print $1 "\t" $2 "\t\t" $6}'
SNMP table:
ifIndex ifDescr ifPhysAddress
1 lo up
2 ens33 0:c:29:53:aa:c6
3 virbr0 52:54:0:e6:6b:2f
4 virbr0-nic 52:54:0:e6:6b:2f
When we check under CentOS 7 we get
ifconfig
ens33: ... mtu 1500
inet 192.168.174.128 netmask 255.255.255.0 broadcast 192.168.174.255
inet6 ...
ether 00:0c:29:53:aa:c6 netmask 255.0.0.0
...
lo: ... mtu 65536
inet 127.0.0.1
...
virbr0: ... mtu 1500
inet 192.168.122.1 netmask 255.255.255.0 broadcast 192.168.122.255
ether 52:54:00:e6:6b:2f ...
...
Bonus shell command:
snmptranslate -Oaf IF-MIB::ifTable
.iso.org.dod.internet.mgmt.mib-2.interfaces.ifTable
and
snmptranslate -Oaf IP-MIB::ipAddrTable
.iso.org.dod.internet.mgmt.mib-2.ip.ipAddrTable
I do not know why/if there is a single table holding both information.
For example, on the physical machine:
# ip addr
5: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 ..
inet 10.32.230.90/24 scope global eth2
valid_lft forever preferred_lft forever
inet 10.32.230.61/24 scope global secondary eth2
valid_lft forever preferred_lft forever
8: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500
link/ether 02:42:65:1b:b0:25 brd ff:ff:ff:ff:ff:ff
inet 172.17.42.1/16 scope global docker0
"10.32.230.90" is the main IP of this machine, and "10.32.230.61" is secondary added with "ip addr add 10.32.230.61/24 dev eth2".
After creating a docker instance, with IP = 172.17.0.10, I add the following rules to connect native IP with secondary IP:
# iptables -A POSTROUTING -j MASQUERADE
# iptables -t nat -A PREROUTING -d 10.32.230.61 -j DNAT --to 172.17.0.10
# echo 1 > /proc/sys/net/ipv4/ip_forward
But it doesn't work because external PC still cannot get access to 10.32.230.61, but can get access to 10.32.230.90. What's the solution?
(From a certain PC, which IP is, for example, 10.32.230.95)
# ping 10.32.230.90
PING 10.32.230.90 (10.32.230.90) 56(84) bytes of data.
64 bytes from 10.32.230.90: icmp_seq=1 ttl=52 time=280 ms
64 bytes from 10.32.230.90: icmp_seq=2 ttl=52 time=336 ms
^C
# ping 10.32.230.61
(Timeout..)
I am sure that there is no IP confliction: 10.32.230.61 is not used by any other hosts.
I want to replace ifconfig with /sbin/ip. Using ifconfig I can see lines like
inet addr:xx.xxx.x.xx Bcast:xx.xxx.x.xx Mask:255.255.255.0
and can easily parse this to find the netmask (255.255.255.0). How can I achieve this using /sbin/ip?
Running ip a you'll get output similar to that which you get running ifconfig. Specifically, you'll see a line similar to yours:
inet xx.xxx.x.xx/24 brd xx.xxx.x.xx
The /24 denotes the subnet mask in slash notation.
I'm testing IPv6 networking (using FreeBSSD .0, VMWare, NAT), but I can't connect from outside (localhost) via an IPv6 address(using IPv4, it works fine). How can I set up the network properly?
[root# /home/osmund]# cat /etc/rc.conf
hostname=""
ipv6_activate_all_interfaces="YES"
ifconfig_em1_ipv6="inet6 2001:db8:1::1 prefixlen 64"
#ipv6_enable="YES"
ipv6_network_interface="em1"
ifconfig_le0="DHCP"
sshd_enable="YES"
# Set dumpdev to "AUTO" to enable crash dumps, "NO" to disable
dumpdev="AUTO"
[root# /home/osmund]# ifconfig
em1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=8<VLAN_MTU>
ether 00:0c:29:8f:45:74
inet6 2001:db8:1::1 prefixlen 64
inet6 fe80::20c:29ff:fe8f:4574%em1 prefixlen 64 scopeid 0x2
inet 192.168.124.133 netmask 0xffffff00 broadcast 192.168.124.255
nd6 options=23<PERFORMNUD,ACCEPT_RTADV,AUTO_LINKLOCAL>
media: Ethernet autoselect
status: active
plip0: flags=8810<POINTOPOINT,SIMPLEX,MULTICAST> metric 0 mtu 1500
nd6 options=23<PERFORMNUD,ACCEPT_RTADV,AUTO_LINKLOCAL>
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384
options=3<RXCSUM,TXCSUM>
inet6 ::1 prefixlen 128
inet6 fe80::1%lo0 prefixlen 64 scopeid 0x4
inet 127.0.0.1 netmask 0xff000000
nd6 options=23<PERFORMNUD,ACCEPT_RTADV,AUTO_LINKLOCAL>
[root# /home/osmund]# ping6 2001:db8:1::1
PING6(56=40+8+8 bytes) 2001:db8:1::1 --> 2001:db8:1::1
16 bytes from 2001:db8:1::1, icmp_seq=0 hlim=64 time=0.529 ms
16 bytes from 2001:db8:1::1, icmp_seq=1 hlim=64 time=0.133 ms
^C
--- 2001:db8:1::1 ping6 statistics ---
2 packets transmitted, 2 packets received, 0.0% packet loss
round-trip min/avg/max/std-dev = 0.133/0.331/0.529/0.198 ms
[root# /home/osmund]#
Have you tried to use bridged network instead?