Questions tagged [rfc]
A Request for Comments (RFC) is a publication of the Internet Engineering Task Force (IETF) and the Internet Society, the principal technical development and standards-setting bodies for the Internet.
108
questions
1
vote
2
answers
106
views
Abuse of Abuse reporting system / Feedback loop by spfbl.net
We are getting below abuse emails from Abuse reporting system / Feedback loop by spfbl.net
Can someone explain how are these even valid Abuse emails in any sense at all, because they are clearly being ...
- 19
0
votes
1
answer
374
views
DHCP renewal can't go through because DHCP server is down
To my experience, if a DHCP client tries to renew its lease, but the DHCP server is down, and after the lease time is over, there are two possible scenarios:
The client keeps the IP
The client goes ...
- 373
1
vote
1
answer
420
views
is "GET /" a valid HTTP request?
I noticed that sending GET / (+CRLF) to some webservers (e.g. from a well-known search provider) results in a HTTP/1.0 200 OK message. Other webserver respond with a HTTP/1.0 400 error.
To my ...
- 13
1
vote
1
answer
253
views
Is it legal for a DHCP relay agent to relay RENEWAL requests that were directly unicast to the "Server identifier" server?
I'm observing the following in a packet capture.
Client -> Broadcast : DHCP Request
Relay -> Client : DHCP Ack (Option 54 == Server)
... After T1 expires ...
Client -> Server Identifier ...
- 111
1
vote
0
answers
119
views
RFC 3074 DHCP Load Balancing STID vs RFC 2131 DHCP xid
Section 2.2 of RFC 3074 defines a Service Transaction ID (STID) as:
An attribute of the individual client requests used for load-balancing.
However, section 2 of RFC 2131 defines the xid field of a ...
- 23
7
votes
1
answer
2k
views
Which ICMP types (v4/v6) should not be blocked?
I have made a lot of research into this and have found that some references contradict each other.
IPV6
For example RFC4890 says the following types should be allowed for optimal functionality:
Type ...
- 1,695
0
votes
1
answer
5k
views
syslog-ng: how to configure sending RFC5424 messages with octet-counting framing
Please don't bother reading this question. syslog-ng is already set up to send RFC5424 messages with octet-counting framing by default. I was confused by the behaviour of another component. This ...
- 393
0
votes
2
answers
90
views
Doubts about DKIM verification (RFC6376)
Good morning,
https://www.rfc-editor.org/rfc/rfc6376#section-5 reads:
"Survivability of signatures after transit is not guaranteed, and
signatures can fail to verify through no fault of the ...
- 107
3
votes
0
answers
123
views
Why not shorten a single :0000: field in IPv6
rfc5952, section 4.2.2 "Handling One 16-Bit 0 Field" goes:
The symbol "::" must not be used to shorten just one 16-bit 0 field. For example, the representation
2001:db8:0:1:1:1:1:...
3
votes
2
answers
2k
views
How can DHCPv6 server allocate fixed IPv6 addresses to clients if it's not allowed to interpret DUID?
According to RFC3315:
Each DHCP client and server has a DUID. DHCP servers use DUIDs to
identify clients for the selection of configuration parameters and in
the association of IAs with clients. DHCP ...
- 398
-1
votes
2
answers
387
views
Do glue records/child hosts override DNS wildcard entries or A records at the domain names DNS servers records?
Do glue records/child hosts override DNS wildcard entries or A records at the domain names DNS servers records?
example:
ns1.example.com = 1.1.1.1 at registrar DNS glue /child host
ns1.example.com = 2....
- 109
0
votes
1
answer
76
views
Two way handshake for WHOIS protocol? RFC 3912
From RFC 3912:
3. Protocol Example
If one places a request of the WHOIS server located at whois.nic.mil
for information about "Smith", the packets on the wire will look
like:
client ...
1
vote
1
answer
3k
views
IPv6 address text notation with prefix: inside or outside square brackets?
I'm skimming through some IPv6 related RFCs. Some claim that a prefix should be written outside of the square brackets, whereas others have it tacked on to the address directly.
Specifically, RFC4291, ...
- 487
0
votes
1
answer
411
views
DHCPv6 (RFC 8415) - What are reasonable initial values for time intervals T1/T2?
As described in Section 18.2. - Client Behavior of DHCP - RFC 8415 a client uses the Solicit message to discover DHCP servers configured to assign leases or return other configuration parameters on ...
- 115
0
votes
1
answer
93
views
Where to find symbol definitions for RFC protocol flow diagram?
I am reading RFC5077, and bumped into following diagram:
ClientHello
(empty SessionTicket extension)-------->
ServerHello
...
- 105
1
vote
1
answer
3k
views
Master ipv4 CIDR configuration for private cluster in GCP
I'm trying to create a private cluster in GCP as per the steps mentioned here:
https://cloud.google.com/kubernetes-engine/docs/how-to/private-clusters
As per this, the ipv4 address for the master ...
google-cloud-platform
0
votes
1
answer
361
views
RFC 5321 requires my SMTP server with the Enhanced-Status-Codes service extension to reply with “250 OK”
RFC 2034
4. The Enhanced-Status-Codes service extension
Servers supporting the Enhanced-Status-Codes extension must preface
the text part of almost all response lines with a status code. As in
...
- 105
3
votes
1
answer
4k
views
How is truncation performed in DNS according to RFC 1035?
I'm trying to implement my own DNS server from scratch. However, I'm having difficulty understanding how RFC 1035 recommends truncation to be performed.
Section 6.2 says:
When a response is so long ...
- 235
2
votes
3
answers
1k
views
Message-ID of delivery report is equal to original mail
I discoverd that the delivery status report has the same message-id as the original mail.
Here is the text of the delivery report:
Incoming DSN message:
From: Mail Delivery Subsystem <postmaster@...
- 3,963
2
votes
1
answer
2k
views
How to block this range of RFC1918 on Ubuntu server?
We're running an IKEv2 VPN on a Ubuntu server. One of our users has run a NetScan while using our VPN, which has upset the server provider.
This is what the server provider has recommended:
We would ...
- 1,695
0
votes
1
answer
159
views
rfc3207 smtp starttls restriction confusion
From https://www.rfc-editor.org/rfc/rfc3207:
A publicly-referenced SMTP server MUST NOT require use of the
STARTTLS extension in order to deliver mail locally.
This rule (1.) prevents the STARTTLS ...
- 349
-3
votes
1
answer
417
views
Same Interface routing with ICMP-Redirect disabled? [closed]
I don't want to talk around the bush for long. I disagree with a friend how a router would behave in a special configuration. Unfortunately I can't test it here to check my point of view. Specifically,...
- 7
4
votes
1
answer
101
views
Should I reject mail to test domains?
RFC6761 states about example domains (such as example.com):
Application software SHOULD NOT recognize example names as special and SHOULD use example names as they would other domain names.
...
- 1,276
3
votes
1
answer
676
views
TLS Implementation/RFC interpretation
Does the Server Hello break the RFC? There seems to be contradiction in RFC.
A customer claims our device (Citrix Netscaler) returns Extension (ec_point_formats: EC point format: uncompressed) when ...
- 1,048
0
votes
1
answer
1k
views
Is it possible DNS packet contains more than one SOA resource record
I've read RFC 1034 and RFC 1035 to learn about DNS protocol standards. I'm searching to find a limit occurring of SOA resource records. I'm aware that A, AAAA, CNAME, NS, MX, TXT RRs have no limit. ...
- 103
2
votes
1
answer
2k
views
LDAPS Microsoft Active Directory Multiple Certificates RFC6125
We have an Microsoft Active Directory Domain with a large pool of domain controllers (DC) that are are setup with LDAP. These are all setup with LDAPS and uses Certificate Services via a template to ...
- 173
1
vote
0
answers
210
views
Is there any IETF / RFC standard defined for hosts file encoding?
While going through the accepted answer for hosts file ignored, how to troubleshoot?, I observed the statement "The hosts file should encoded in ANSI or UTF-8 without BOM". As I personally faced ...
- 133
3
votes
1
answer
6k
views
Which characters/values are allowed to use in DNS?
While I was looking on RFCs of DNS because of implementation to check underscore in CNAME records, I found this interesting discussion and RFC with interesting point:
https://www.ietf.org/mail-...
- 31
1
vote
1
answer
307
views
Which side of this SMTP conversation is correct?
I have an odd scenario with two mail servers communicating with one another and need help determining which one is behaving correctly.
It's a little complicated to explain, so I think a SMTP ...
- 12.1k
-1
votes
1
answer
688
views
Can a non-authoritative name server give any response it likes to?
Our domain registrar allows us to either make use of our own DNS servers or to use theirs (configuring DNS entries in their web interface); I suppose this is a common situation.
We have opted to set ...
- 119
0
votes
1
answer
1k
views
Special characters in mail (address) headers and RFC2047 encoding
I have some unexpected handling of RFC2047 "From" headers on Exim.
(Actual addresses have been changed, the original display name contained non-ASCII characters)
For this "From" ...
1
vote
1
answer
214
views
Why IPs from the Private Address Space would be reachable through public network, and what customers can do about it?
Scenario:
I have a customer running a Win7 Pro and an OpenVPN client; this workstation is used from one of their employees to send remote cmds to the (Windows) OpenVPN server, both using psexec and ...
- 1,729
0
votes
1
answer
15k
views
Yahoo Mail: "No mx record found for domain"
Yahoo's Mail servers are refusing to deliver messages to the mail server for a domain I manage. It complains that there is no MX record for the domain. According to my understanding for many years, ...
- 171
0
votes
1
answer
784
views
Email format RFCs
I know there are lots of RFCs that changed how an email can be made. However, most of the RFCs don't apply to for example outlook.
First of all, what are RFCs exactly? And why don't for example ...
- 403
2
votes
1
answer
8k
views
Rejected emails: Messages with multiple addresses in From: header are not accepted - gsmtp
We host a service which can send emails on behalf of client businesses to end users. These emails must appear to be from the client business, even though they are generated from within our system.
We ...
0
votes
1
answer
705
views
To-Recipient Required in Email?
I would like to know if a "To"-Recipient is required in an e-mail per definition or if all recipients could be Bcc or Cc.
RFC5322 states
The only required header fields are the origination date ...
- 103
2
votes
2
answers
106
views
why can the Sender field not be easily configured?
To clarify this and this explanation for Sender::
In brief, From: in the message indicates the mailbox of whoever wrote
the message, Sender: indicates the entity which sent a message on
behalf ...
- 229
16
votes
2
answers
2k
views
What's the point of repeating an email address in "The Envelope" and the "The Header"?
I learned that both the FROM address and the TO address is repeated in a hidden element called the "envelope", and then repeated again in the "body".
Question
Why isn't the envelope data copied into ...
- 311
1
vote
1
answer
92
views
Does a ccTLD/gTLD give out response from cache (or use cache)?
The question is exactly the same as the title says. Does the ccTLD/gTLD (and root servers come into the scenario automatically i presume) use cache?
And what type of response it supplies?
I know ...
- 13
1
vote
1
answer
453
views
Debate with Microsoft on RFC 1918 when setting up a VPN to Azure
Microsoft has a technology called "point to site" VPN. (reference1, reference2)
I have the following internal class "A" networks defined on premise:
10.2.0.0/16
10.4.0.0/16
10.40.0.0/16
10.20.0.0/...
- 8,983
1
vote
1
answer
1k
views
What is the format of the NAME field in the DNS answer section?
The NAME field is not detailed completely in RFC 1035 section 4.1.3.
I want to understand this field (programmatically) for the ANSWER message type and I searched these resources (datasheet) for that....
- 244
7
votes
2
answers
15k
views
Why isn't net.ipv4.tcp_rfc1337 enabled by default?
The tcp_rfc1337 setting seems to have a solution for TIME-WAIT Assassination.
The first problem is that old duplicate data may be accepted erroneously in new connections, leading to the sent data ...
- 673
2
votes
3
answers
4k
views
Creating a RFC 1123 compliant date for HTTP header creation on the CLI
I'm trying to create a HTTP 1/1 compliant date header using standard unix date(1) in order to post this to a RESTful server using curl or similar.
Any ideas what format to pass to date(1) to get this ...
- 289
0
votes
0
answers
45
views
IMAP woes when moving to new Exchange
We've recently moved to a semi-outsourced Exchange farm, replacing our internal one. An application I've been asked to help troubleshoot uses IMAP to download some emails from the Exchange servers in ...
11
votes
2
answers
3k
views
RFC that requires DNS servers to respond to unknown domain requests
My domain registrar and DNS provide currently ignores DNS requests to unknown domains. By ignore I mean black-holes and never responds which causes my DNS clients and resolver libraries to retry, ...
- 579
45
votes
2
answers
3k
views
Which RFCs should be cited as internet standards?
It's extremely common for RFCs to be cited in support of opinions (including Serverfault Q&A's), but the average IT employee has a very poor understanding in regards to which RFCs define standards ...
- 33.3k
1
vote
1
answer
1k
views
Sendmail support of empty group addresses (AKA list syntax)
E-mail group addresses such as undisclosed-recipients:; or a group:<[email protected]>,<[email protected]>; are valid forms of addressing according to RFC 5322, see for instance the ...
- 363
-1
votes
2
answers
49
views
Is RFC1035s definition of a <domain-name> wrong?
[RFC1035] defines <domain-name> as
<domain-name> is a domain name represented as a series of labels, and
terminated by a label with zero length.
This means a <domain-name> must be a ...
- 117
19
votes
2
answers
5k
views
Why is RFC 7505 (Null MX) necessary?
IETF RFC 7505 describes MX records for a domain/host that explicitly should not receive email. This is accomplished by pointing the MX at the Domain Name System root. For example,
nomail.example.com. ...
- 193
1
vote
2
answers
607
views
Is smart hosting to an A record a violation of RFC-5321 section 1?
I have a sendmail server configured to smarthost to a downstream resource. The configuration is currently:
define(`SMART_HOST',`relay:[vip.example.local]')dnl
Since it's sending the A record for ...
- 12.1k