Dieses Jahr versuchen wir uns auf vielfachen Wunsch an einem noch praktischer orientierten Grundlagen-Vortrag. Wir fangen an bei Verkabelung (Kupfer, Glasfasern, Stecker, etc.), gehen weiter zu Ethernet (STP, VLANs, LAGs / Bonding) und enden unseren Ausflug bei IP und Grundlagen des Debugging (Ping, Traceroute).

1. Angewandte Netzwerkgrundlagen reloaded
Von Layer 1 bis 3
FrOSCon 15 - Cloud Edition
Falk Stern, Maximilian Wilhelm
1 / 64

2. Agenda
1. Who's who
2. Models
3. Layer 1
4. Layer 2 (Ethernet)
1. LAGs / Bonding
2. VLANs
5. Layer 3 (IP)
2 / 64

3. Who's who Falk Stern
Full Stack Infrastructure Engineer
IPv6 fanboy
Runs his own Kubernetes cluster in his basement
Consultant @ Profi Engineering Systems AG
Contact
@wrf42
falk@fourecks.de
3 / 64

4. Who's who Maximilian Wilhelm
Infrastructure Engineer
OpenSource Hacker
Fanboy of
(Debian) Linux
IPv6
Occupation:
By day: Senior Infrastructure Architect, Uni Paderborn
By night: Infrastructure Archmage, Freifunk Hochstift
In between: Freelance Solution Architect for hire
Contact
@BarbarossaTM
max@sdn.clinic
4 / 64

5. Who's who
Models
Layer models - ISO/OSI, TCP/IP & Hybrid
5 / 64

6. Who's who
Models
Layer models - ISO/OSI, TCP/IP & Hybrid
Physical
Wires, Wireless - 802.3 & 802.11 (Bit)
Data Link
Addressing stations on the same physical medium (Ethernet MAC) (Frame)
Network
Adressing stations somewhere in the entire network (IPv4, IPv6) (Packet)
Transport
How to transport data? (Datagram, Segment)
Session, Presentation, Application
Which data to transport? (SSH, IRC, HTTP, etc.)
6 / 64

7. Who's who
Models
Layer 1
Layer 1 - Physical networking*
* for Ethernet 7 / 64

8. Who's who
Models
Layer 1
Air
802.11ac
802.11ax
Real copper cables
Usually Category 7 today
Category 6a is usually fine
Fiber
Multi mode fiber (MMF)
Single mode fiber (SMF)
Specials
Direct Attached Cable (DAC)
Active Optical Cable (AOC) Source: Wikimedia commons
The medium is the message
8 / 64

9. Who's who
Models
Layer 1
Wireless
Looks like Ethernet (802.3) but isn't
Differentiates between Stations (STA) and Access Points (AP)
Generation Max Linkrate Frequency
Wi-Fi 1 (802.11b) 1 - 11 Mbit/s 2.4 GHz
Wi-Fi 2 (802.11a) 1.5 - 54 Mbit/s 5 GHz
Wi-Fi 3 (802.11g) 3 - 54 Mbit/s 2.4 GHz
Wi-Fi 4 (802.11n) 72 - 400 Mbit/s 2.4 & 5 GHz
Wi-Fi 5 (802.11ac) 433 - 6933 Mbit/s 2.4 & 5 GHz
Wi-Fi 6 (802.11ax) 600 - 9608 Mbit/s 2.4 & 5 GHz, 1-6 GHz ISM
9 / 64

10. Who's who
Models
Layer 1
Wireless
Channels between 20 and 160 MHz
Channels usually overlap
2.4 GHz is dead, as well as 802.11abg
Problem with 5 GHz Channels is Radar DFS (Dynamic Frequency Selection)
Channelwidths above 20 MHz only usable in 5 GHz bands
10 / 64

11. Who's who
Models
Layer 1
Wireless Encryption
Started with a 40 Bit WEP key, 104 bit did cost extra
Currently WPA3 with PSK or EAP
EAP usually authenticates against a RADIUS server
PSK is "safe enough" for home use
11 / 64

12. Who's who
Models
Layer 1
Twisted Pair copper cables
https://en.wikipedia.org/wiki/2.5GBASE-T_and_5GBASE-T 12 / 64

13. Who's who
Models
Layer 1
Types of fibers
Multi mode fiber
Single mode fiber
Form factors of connectors
ST
SC
LC
E2000
MTO/MTP
Contact of connectors
PC
APC
Let's talk about bers
13 / 64

14. Who's who
Models
Layer 1
Usually used at 850nm
Attenuation between 1,5 - 3dB/km
Only suited for shorter ranges
Light is bouncing off the "edges"
Category Color code Fiber type
OM1 orange G62,5/125
OM2 orange G50/125
OM3 aqua G50/125
OM4 violet G50/125
OM5 lime G50/125
Acceptance
cone
Cladding
Cladding
Core
Multi mode ber (MMF)
https://de.wikipedia.org/wiki/Lichtwellenleiter#Multimodefaser 14 / 64

15. Who's who
Models
Layer 1
Usually used between 1270nm &
1610nm
Attenuation 0,4 - 1,0dB/km
Suited for long range connections
Light travels "straight"
Category Color code Fiber type
OS1 yellow E9/125
OS2 yellow E9/125
Single mode ber (SMF)
15 / 64

16. Who's who
Models
Layer 1
Maximum ber lengths*
Multi mode values depending on category!
The following values ignore
Use of amplifiers
Use of WDM
Number of patches
Connector types
Contact types
Speed Multi mode Single mode
1Gb/s ≤1000m ≤ 1km
10Gb/s ≤ 500m ≤ 80km
40Gb/s ≤ 150m ≤ 80km
100Gb/s ≤ 100m ≤ 80km
* This is a very rough overview 16 / 64

17. Who's who
Models
Layer 1
ST / Straight Tip (1992)
Still seen in the wild
Legacy infrastructure
SC / Standard connector (1993)
Used on older optics
Still in wide use on panels
24 duplex ports per RU
LC / Lucent/Little connector (2002)
De facto standard today
In wide use on optics & panels
48 duplex ports per RU
Common optical ber connectors
17 / 64

18. Who's who
Models
Layer 1
E2000 / LSH (1997)
Dust caps included
prevents you from looking into
the beam
More expensive
Usually used for MAN/WAN links
Multiple-Fiber Push-On/Pull-off
(MPO/MTP)
Connects up to 24 cores
Usually used within data centers
e.g. rear connection for panels
Source (MTP): Wikimedia commons
Common optical ber connectors (contd.)
18 / 64

19. Who's who
Models
Layer 1
Physical contact (PC)
Slightly convex surface
Mostly blue connectors bodies
Angled physical contact (APC)
Fiber end face polished at 8° angle
Green connector body
Contact type usually denoted as suffix:
LC/PC
E2000/APC
Common optical connectors / contact
https://en.wikipedia.org/wiki/Optical_fiber_connector#Contact 19 / 64

20. Who's who
Models
Layer 1
Transceivers
1Gb/s
GBIC
SFP
10Gb/s
Xenpak
X2
XFP
SFP+
25Gb/s
SFP28
40Gb/s
QSFP+
100Gb/s
CFP
QSFP28
400Gb/s
DD-QSFP
Transceivers - It's not all GBICs
20 / 64

21. Who's who
Models
Layer 1
Transceivers
Gigabit interface converter (GBIC)
old and busted (1995)
obsoleted by SFP
connector
RJ45
SC
proprietary
supported speeds:
1Gb/s
Transceivers - GBICs
21 / 64

22. Who's who
Models
Layer 1
Transceivers
Small form-factor pluggable (SFP)
introduced 2001
aka Mini-GBIC
connector
RJ45
LC
supported speeds
100Mb/s
1Gb/s
Transceivers - SFPs
https://en.wikipedia.org/wiki/Small_form-factor_pluggable_transceiver 22 / 64

23. Who's who
Models
Layer 1
Transceivers
introduced 2001
obsoleted by X2, XFP, SFP+
connectors
SC
CX4
converter to SFP+
supported speeds:
10Gb/s
Transceivers - XENPAK
23 / 64

24. Who's who
Models
Layer 1
Transceivers
introduced 2002
slightly smaller than XENPAK
consume less power than XENPAK
obsoleted by XFP, SFP+
connectors
SC
CX4
converter to SFP / SFP+
supported speeds:
1Gb/s (via converter)
10Gb/s
Transceivers - X2
24 / 64

25. Who's who
Models
Layer 1
Transceivers
introduced 2002/2003
much smaller than X2
slightly larger than SFP(+)
obsoleted by SFP+
connectors
LC
supported speeds:
10Gb/s
Source: Wikimedia commons
Transceivers - XFP
25 / 64

26. Who's who
Models
Layer 1
Transceivers
introduced 2006
much smaller than XENPAK, X2
slightly smaller than XFP
same size as SFP
compatible to SFP
connectors:
RJ45
LC
DAC
AOC
supported speeds:
1Gb/s
10Gb/s
Transceivers - SFP+
26 / 64

27. Who's who
Models
Layer 1
Transceivers
Quad SFP+
4 channels of 10Gb/s
slightly larger than SFP
fanout possible to 4x 10Gb/s
connectors:
LC
MTO/MTP
DAC
AOC
supported speeds:
10Gb/s
40Gb/s
Transceivers - QSFP+
27 / 64

28. Who's who
Models
Layer 1
Transceivers
4 channels of 28Gb/s
same size as QSFP(+)
compatible to QSFP+
fanout possible to
4x 10Gb/s
4x 25Gb/s
connectors:
LC
MTO/MTP
DAC
AOC
supported speeds:
10Gb/s
25Gb/s
40Gb/s
100Gb/s
Transceivers - QSFP28
28 / 64

29. Who's who
Models
Layer 1
Transceivers
one channel of 28Gb/s
same size as SFP(+)
compatible to SFP+
connectors:
LC
DAC
AOC
supported speeds:
1Gb/s
10Gb/s
25Gb/s
Transceivers - SFP28
29 / 64

30. Who's who
Models
Layer 1
Transceivers
Double-density Quad-SFP
8 channel of 50Gb/s
same size as QSFP*
fanout possible to
4x 100Gb/s
connectors:
LC
DAC
AOC
MTO/MTP
supported speeds:
400Gb/s
Transceivers - DD-QSFP
30 / 64

31. Who's who
Models
Layer 1
Outlook - CWDM
Coarse Wavelength Division Multiplexing
Using different wavelength on the same fiber
https://community.fs.com/de/blog/wdm-technology-basis-cwdm-vs-dwdm.html 31 / 64

32. Who's who
Models
Layer 1
Outlook - CWDM
Coarse Wavelength Division Multiplexing
Using different wavelength on the same fiber
Requires transceiver with specific "color"
https://community.fs.com/de/blog/wdm-technology-basis-cwdm-vs-dwdm.html 32 / 64

33. Who's who
Models
Layer 1
Copper based cable of fixed length
Transceiver permanently attached
SFP+/SFP28
QSFP/QSFP28
Available from 1Gb/s to 400Gb/s
Pros:
Much cheaper than fiber link
Simple
Cons:
Only useful within one / between
adjacent racks
Slightly higher latency
Susceptible for EM interference
Specials - Direct Attached Cable (DAC)
33 / 64

34. Who's who
Models
Layer 1
Specials - Active Optical Cable (AOC)
Fiber based cable of fixed length
Transceiver permanently attached
SFP+/SFP28
QSFP+/QSFP28
DD-QSFP
Available from 10Gb/s to 400Gb/s
Pros:
Slightly less attenuation than manual optical connection
At higher bandwidth cheaper than transceiver + cable
Cons:
Only useful within one / between adjacent racks
34 / 64

35. Who's who
Models
Layer 1
Layer 2 Layer 2 - Ethernet
35 / 64

36. Who's who
Models
Layer 1
Layer 2
Ethernet
Developed between 1973 and 1974 at Xerox
Inspired by ALOHAnet, the Packet Radio Network on Hawaii
At first available with 2,94 Mbps, 10 Mbps available commercially since 1980
Further development lead to IEEE standard 802.3 in 1983
CSMA/CD - "Carrier Sense, Multiple Access, Collision Detect"
Ethernet today:
Common access port speed: 1 Gbit/s
Common uplink/server interfaces speed: 10 - 40 Gbit/s
Up to 400-Gbit/s available commercially
Interfaces for copper or multi-mode / single-mode fiber
Preamble SFD
Source
MAC
Address
Destination
MAC
Address
EtherType FCSPayload
Source: Wikimedia Commons
36 / 64

37. Who's who
Models
Layer 1
Layer 2
Ethernet Technology
Repeater
Maximum Segmentlength in on network segment around 100m
Repeater amplify and repeat signals
Extend broadcast domains
Extend collision domains
Bridges
Extend broadcast domains
Limit collision domains
Important Rule: Frames must not be send out on port where they were received
37 / 64

38. Who's who
Models
Layer 1
Layer 2
Ethernet Devices
Hubs
Repeater with many ports
Switches
Bridges with many ports
Three possible actions to happen with any frame:
Forward
Replicate
Drop
38 / 64

39. Who's who
Models
Layer 1
Layer 2
Addresses
Format: AA:BB:CC:DD:EE:FF
Identify stations on the same physical medium
Should be unique (on the medium)
1st octet 2nd octet 3rd octet 4th octet 5th octet 6th octet
6 octets
or
Organisationally Unique
Identifier (OUI)
Network Interface Controller
(NIC) Specific
3 octets 3 octets
b7 b6 b5 b4 b3 b2 b1 b0
8 bits
0:
1:
unicast
multicast
0:
1:
globally unique (OUI enforced)
locally administered
Source: Wikipedia Commons
39 / 64

40. Who's who
Models
Layer 1
Layer 2
Linux command line example
$ ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue
state UNKNOWN mode DEFAULT group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast
state DOWN mode DEFAULT group default qlen 1000
link/ether 70:5a:0f:cf:21:f3 brd ff:ff:ff:ff:ff:ff
3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq
state UP mode DORMANT group default qlen 1000
link/ether 64:80:99:cf:66:6f brd ff:ff:ff:ff:ff:ff
11: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1400 [...]
link/none
40 / 64

41. Who's who
Models
Layer 1
Layer 2
Spanning Tree
Protocol for loop prevention within ethernet networks
Create logical tree of network topology based on BPDUs
Will block connections which will produce loops
Only deactivate STP if you really know better
Seriously!
41 / 64

42. Who's who
Models
Layer 1
Layer 2 Layer 2 / LAGs
42 / 64

43. Who's who
Models
Layer 1
Layer 2
LAGs
Link Aggregation
Combine one or more physical links between two peers to one virtual link, to
increase over-all bandwidth
create a redundant Layer 2 link
both
Also know as:
LAG
Bonding (Linux)
Aggregated Ethernet (Juniper)
Port-Channel (Cisco)
Trunk (3Com, HP?)
NIC-Teaming
43 / 64

44. Who's who
Models
Layer 1
Layer 2
LAGs
Link Aggregation - Simple Linux bonding
Just use multiple links and hope the peer does, too.
Drawbacks:
If media converters are involved a link-down event may not propagate
No way to tell it the peer is configured the same way
44 / 64

45. Who's who
Models
Layer 1
Layer 2
LAGs
Link Aggregation - LACP
Link Aggregation Control Protocol (802.3ad / 802.1AX)
De-facto standard within networking world
Use LACP signalling to set up LAG with peer
Maximum of 8 interface per LAG
Keep alive every 1s (fast) or every 30s (slow)
An interface can be on one of two modes:
active: send out LACP packets to activly form the LAG
passive: wait for and only then reply to LACP packets
45 / 64

46. Who's who
Models
Layer 1
Layer 2
LAGs
Multi-Chassis Link Aggregation Groups
Link Aggregation between more than two peers
At least on peer has to do magic to make this work
Also know as:
MC-LAG
MLAG
Virtual Port-Channel (vPC)
Source: Wikipedia
46 / 64

47. Who's who
Models
Layer 1
Layer 2
LAGs
Loadbalancing Tra c over LAGs
Round-Robin
One packet on link 1, one on link 2, ..., and repeat
Hashing of header elds
Layer 2 (src MAC + dst MAC)
Only useful if communication is to multiple stations within local subnet
Layer 2+3 (src MAC + dst MAC + src IP + dst IP)
Might be more useful for communication without local subnet
Layer 3+4 (src IP + dst IP + src Port + dst Port)
Probably most useful when communicating with multiple peers
47 / 64

48. Who's who
Models
Layer 1
Layer 2
LAGs
Layer 2 / VLANs
48 / 64

49. Who's who
Models
Layer 1
Layer 2
LAGs
VLANs
Virtual Local Area Networks (VLANs)
Used to separate broadcast domains in LANs
VLAN transport between switches standardized as IEEE 802.1q
after proprietary standards from Cisco, 3COM
12 bit VLAN Identifier
only 4096 possible VLANs, ~100 reserved for internal switch functions
1 2 3 4 5 6
Destination MAC
1 2 3 4 5 6
Source MAC
1 2 3 4
802.1Q Header
TPID=0x8100 PCP/DEI/VID
1 . . . n
Payload
1 2
EtherType/
Size
1 2 3 4
CRC / FCS
1 2 3 4 5 6
Inter Frame Gap
7 8 9 10 11 12
1 2 3 4 5 6
Destination MAC
1 2 3 4 5 6
Source MAC
1 . . . n
Payload
1 2
EtherType/
Size
1 2 3 4
CRC / FCS
1 2 3 4 5 6
Inter Frame Gap
7 8 9 10 11 12
n = 42–1500
n = 46–1500
1 2 3 4 5 6
Preamble
7 8
SFD
1 2 3 4 5 6
Preamble
7 8
SFD
49 / 64

50. Who's who
Models
Layer 1
Layer 2
Layer 3
Layer 3 / IPv4
50 / 64

51. Who's who
Models
Layer 1
Layer 2
Layer 3
IPv4 Adresses
Identify stations within and beyond subnets
Up to - but not limited to - the Internet
32bit long
Composed of 4 octets
127.0.0.1
192.168.178.42
Subdived into network and host part
What is now known as the Internet started as a research project in the 1970s to
design and develop a set of protocols that could be used with many different
network technologies to provide a seamless, end- to-end facility for
interconnecting a diverse set of end systems.
Source: RFC4632, Section 2
51 / 64

52. Who's who
Models
Layer 1
Layer 2
Layer 3
Network Classes (historical!)
Deprecated since 1993 (RFC1519)!!1!
Long live CIDR / VLSM
Correct and complete definition given for historical attribution only!
DO NOT USE IN REAL LIFE ANYMORE! SRSLY!
Class Binary Prefix IP Space Default Mask
A 0... 0.0.0.0 - 127.255.255.255 /8
B 10.. 128.0.0.0 - 191.255.255.255 /16
C 11.. 192.0.0.0 - 223.255.255.255 /24
D 1110 224.0.0.0 - 239.255.255.255
E 1111 240.0.0.0 - 255.255.255.255
52 / 64

53. Who's who
Models
Layer 1
Layer 2
Layer 3
Subnetting - CIDR / VLSM
Classless Interdomain Routing
Variable Length Subnet Mask
Introduced in 1993, RFC4632 (original RFC1519)
Prefix Notation -> Number of bits in network part of address
255.255.255.0 == 24 Bit netmask == /24
53 / 64

54. Who's who
Models
Layer 1
Layer 2
Layer 3
Pre xes to know/ Private stu
Loopback
127.0.0.0/8
RFC1918 - Private Address Space
10.0.0.0/8, 172.16.0.0/12 und 192.168.0.0/16
RFC3927 - APIPA / Link-Local
169.254.0.0/16
RFC6598 - Shared Address Space (CGN)
100.64.0.0/10
RFC5737 - Documentation prefixes
192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24
RFC8190 - Special-Purpose IP Address Registries
Complete list of special prefixes
54 / 64

55. Who's who
Models
Layer 1
Layer 2
Layer 3
Linuxcommand line example
$ ip addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 state UNKNOWN [...]
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 state DOWN [...]
link/ether 70:5a:0f:cf:21:f3 brd ff:ff:ff:ff:ff:ff
3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP [...]
link/ether 64:80:99:cf:66:6f brd ff:ff:ff:ff:ff:ff
inet 192.168.178.5/24 brd 192.168.178.255 scope global dynamic wlan0
valid_lft 2450sec preferred_lft 2450sec
inet6 fe80::668:0cff:fecf:666f/64 scope link
valid_lft forever preferred_lft forever
11: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1400 [...]
link/none
inet 10.23.42.8/25 brd 10.23.42.127 scope global ffho-ops
valid_lft forever preferred_lft forever
inet6 fe80::3f59:2a39:b0e1:92ec/64 scope link flags 800
valid_lft forever preferred_lft forever
55 / 64

56. Who's who
Models
Layer 1
Layer 2
Layer 3
ARP - Address Resolution Protocol
Glue between Ethernet and IPv4
Simple protocol to resolve MAC address of IP peer
Two messages types
who-has
is-at
A B
ARP WHO-HAS 192.168.178.8
192.168.178.8 IS-AT 64:80:99:CF:66:6F
A B
56 / 64

57. Who's who
Models
Layer 1
Layer 2
Layer 3
Routing
Every device speaking IP has a routing table
German translation according to IBM: "Leitwegtabelle"
Packets are forwarded according to longest prefix match
Default Gateway or Gateway of last resort used if no entry matches
Hot Potato principle
Packets forwarded to next hop w/o knowledge of their routing table
Asymmetric routing
Path to destination and return path don't have to be identical
57 / 64

58. Who's who
Models
Layer 1
Layer 2
Layer 3
Routing table
Possible routing table of your laptop when using company VPN:
Prefix Iface Next-hop
10.0.0.0/8 tun0 10.23.42.1
10.23.42.0/25 tun0
192.168.178.0/24 wlan0
0.0.0.0/0 wlan0 192.168.178.1
58 / 64

59. Who's who
Models
Layer 1
Layer 2
Layer 3
Source Address Selection
With every routing decision for a locally originated connection a source address is
selected based on the routing table.
Usually the (primary) IP configured on the outgoing interface
May be explicitly set to any IP
For example IP on loopback interface
Prefix Iface Next-hop Src address
10.0.0.0/8 tun0 10.23.42.1
10.23.42.0/25 tun0 10.23.42.8
192.168.178.0/24 wlan0 192.168.178.5
0.0.0.0/0 wlan0 192.168.178.1
59 / 64

60. Who's who
Models
Layer 1
Layer 2
Layer 3
MTU/MSS
Maximum Transmission Unit
Maximum size of a frame
Usually 1500 Bytes in Ethernet networks
Usually >= 9000 Bytes in service provider backbones (Jumbo Frames)
Maximum Segment Size
Maximum size of a segment which fits into a TCP packet
MTU - 60 Bytes
60 / 64

61. Who's who
Models
Layer 1
Layer 2
Layer 3
ICMP - Ping
Echo request / Echo reply messages
Time between request and reply is measured
measures round trip latency
paths can differ
$ ping -c 3 www.heise.de
PING www.heise.de (193.99.144.85): 56 data bytes
64 bytes from 193.99.144.85: icmp_seq=0 ttl=247 time=14.149 ms
64 bytes from 193.99.144.85: icmp_seq=1 ttl=247 time=29.102 ms
64 bytes from 193.99.144.85: icmp_seq=2 ttl=247 time=30.070 ms
--- www.heise.de ping statistics ---
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 14.149/24.440/30.070/7.288 ms
61 / 64

62. Who's who
Models
Layer 1
Layer 2
Layer 3
ICMP - Traceroute
Sends echo requests with increasing TTL
Expects ICMP TTL Exceeded in Transit notifications
$ traceroute kilbeggan.fourecks.de
traceroute to kilbeggan.fourecks.de (88.198.54.132), 64 hops max, 52 byte packets
1 fritz.box (192.168.178.1) 2.243 ms 4.264 ms 14.443 ms
2 192.0.0.1 (192.0.0.1) 8.315 ms 8.309 ms 7.171 ms
3 62.214.38.173 (62.214.38.173) 7.167 ms 10.843 ms 14.588 ms
4 62.214.37.134 (62.214.37.134) 13.658 ms
62.214.37.130 (62.214.37.130) 11.569 ms
62.214.37.134 (62.214.37.134) 14.127 ms
5 versatel-gw.hetzner.com (213.239.239.45) 13.212 ms 12.322 ms 17.035 ms
6 core1.fra.hetzner.com (213.239.245.125) 19.927 ms 22.543 ms
core5.fra.hetzner.com (213.239.224.218) 13.700 ms
7 core23.fsn1.hetzner.com (213.239.229.74) 27.851 ms *
core24.fsn1.hetzner.com (213.239.252.42) 50.545 ms
8 ex9k1.dc13.fsn1.hetzner.com (213.239.245.242) 14.976 ms
ex9k1.dc13.fsn1.hetzner.com (213.239.245.238) 16.691 ms 15.347 ms
9 kilbeggan.fourecks.de (88.198.54.132) 17.902 ms 47.793 ms 22.902 ms
62 / 64

63. Who's who
Models
Layer 1
Layer 2
Layer 3
More?
Future Reading
FrOSCon Network Track 2018:
https://myfirst.network/
Introduction to networking by Ben Eater:
https://www.youtube.com/playlist?
list=PLowKtXNTBypH19whXTVoG3oKSuOcw_XeW
How Autonegotiation works:
https://daemons.net/networking/ethernet/auto-negotiation.html
Alles was ihr schon immer über Glasfasern wissen wolltet:
https://media.ccc.de/v/gpn18-13-alles-was-ihr-schon-immer-ber-glasfasern-wissen-
wolltet
Wie kommt eigentlich das Internet von Hamburg nach Stuttgart
https://media.ccc.de/v/gpn17-8524-
wie_kommt_eigentlich_das_internet_von_hamburg_nach_stuttgart
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64. Who's who
Models
Layer 1
Layer 2
Layer 3
Questions
Questions?
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